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Miscellaneous skin conditions

Miscellaneous skin conditions

 

Acanthosis nigricans

 

This is a relatively common condition, which may be a marker for insulin resistance and occasionally malignancy. Clinically, it presents as hyperpigmented, hyperkeratotic areas that are usually symmetrically distributed in the axillae, the groin, on the neck and in the cubital and popliteal fossae. Multiple skin tags are commonly associated. The mucosal surfaces and the back of the hands and feet may be involved, especially when associated with malignancy.

 

In insulin resistance, the high circulating levels of insulin are thought to stimulate increased growth of keratinocytes by binding to the insulin-like growth factor receptor. Histologically this is manifested as acanthosis and hyperkeratosis. However, the pigmentation does not involve abnormal melanocyte function but is a reflection of the secondary passing on of melanin to a larger population of keratinocytes. In the much rarer malignancy-associated acanthosis nigricans, it seems likely that a humoral factor with a similar action is produced by the tumour.

Malignancy-associated acanthosis nigricans may regress following effective treatment of the underlying cancer. A wide range of malignancies has been reported in association with acanthosis nigricans. The most useful clinical features to suggest this diagnosis include sudden adult onset, lack of obesity or signs of insulin resistance and involvement of mucous membranes and areas other than flexures.

As the most common cause is simple obesity, weight loss can lead to reversal of the skin changes. Exclusion or treatment of the cause of hyperinsulinaemia is mandatory for other patients.

Behçet's disease

 

This is a complex multisystem disease characterised clinically by the presence of oral aphthae and at least two of the following: genital aphthae, synovitis, cutaneous pustular vasculitis, posterior uveitis or meningoencephalitis. The oral aphthae have similar appearances to simple recurrent aphthous ulcers but are often more extensive and more resistant to therapy. Genital aphthae are similar lesions that occur in the genital area, most commonly in the vulva. Recurrent herpes simplex needs to be excluded. Other cutaneous lesions imitate neutrophilic dermatoses such as Sweet’s syndrome, pyoderma gangrenosum or leukocytoclastic vasculitis.

Diagnosis is based on the clinical symptom complex, as there are no diagnostic biopsy or blood findings. Most skin lesions demonstrate a neutrophilic vascular reaction, at least in the early stages. Mucocutaneous and arthritic lesions occur first but eye and neurological involvement are the major causes of morbidity and even death.

First-line treatment of oral aphthae is

lignocaine 2% viscous solution, for the relief of pain

AND

a potent topical corticosteroid applied to ulcers

OR

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, 0.1mL injected into each ulcer.

 

For more severe mucocutaneous disease, use

colchicine 500 microgram orally, 3 times daily

OR

dapsone 50 to 150mg orally, daily.

 

If not responsive, then thalidomide, low-dose methotrexate or a tapered course of prednisolone may be required. Immunosuppression with cyclosporin, azathioprine or interferon is only justified for ocular involvement or severe systemic disease.

 

Epidermoid cyst (sebaceous cyst)

 

An epidermoid cyst is a keratin containing cyst lined by surface epidermis. Clinically, epidermal cysts present as a firm intradermal tumour, mobile over deeper structures and often tethered to the skin, with evidence of a central punctum. However, some cysts may arise following penetration injury and do not have a connection with the overlying epidermis. They are most common on the head, neck and upper trunk. Implantation cysts are more likely to occur on the palms, soles or buttocks. A third form of epidermoid cyst may arise at a plane of embryonic fusion and such midline cysts on the back should raise the possibility of underlying spinal abnormality.

A noninflamed, noninfected cyst is best removed by simple excision. Incision and removal of the contents with the cyst lining also may achieve cure. Inflamed, noninfected cysts can be treated with

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, 0.1 to 0.4mL injected intralesionally.

 

Infected, inflamed cysts are best treated by drainage, culture of the draining material and appropriate antibiotic therapy, commencing initially with antistaphylococcal therapy and modified by culture results.

Erythema nodosum

 

Erythema nodosum represents a distinctive cutaneous response to a variety of apparently unrelated infections and disease processes. Although the mechanism of causation is unknown, there is an increasing suspicion that this represents an antigen-antibody deposition in predominantly the subcutaneous and deep dermal tissues.

The histology characteristically demonstrates a septal panniculitis without evidence of frank vasculitis. The main causes are listed Table1. Clinically, lesions present as erythematous, indurated plaques and nodules on the lower legs, particularly the anterior tibial region. The lesions are painful and resolve over 2 to 3 weeks, with bruising and without any scarring. Less inflammatory and more slowly resolving chronic forms may take months to resolve.

Diagnosis is usually confirmed by biopsy, although classical clinical presentations may not justify the scarring and slow healing often associated with biopsy of inflammatory lesions on the lower legs. A reasonable diagnostic screen includes a full blood count, erythrocyte sedimentation rate, standard biochemical analysis, throat swab, antistreptolysin O titre, antinuclear factor and chest X-ray. Any treatable cause, eg associated tonsillitis, should be treated.

For management of the lesions, first-line therapy is bed rest, elevation of the legs and nonsteroidal anti-inflammatory drugs. Use

ibuprofen 400mg orally, twice daily.

 

If systemic toxicity is severe and there are no contraindications (eg related to the cause), use

prednisolone 50mg orally, daily for 2 weeks with step-wise reduction according to response thereafter.

 

Early ambulation may be assisted by the wearing of compression bandaging or stockings to minimise oedema and discomfort.

bacterial infections	streptococcal, tuberculosis, yersinia
other infections	lymphogranuloma venereum, chlamydia, coccidioidomycosis, histoplasmosis, dermatophytosis, psittacosis
enteropathies	ulcerative colitis, Crohn’s disease
sarcoidosis
drugs	sulfonamides, bromides, oral contraceptives
malignancies	lymphoma, leukaemia

Flushing

 

Blushing is a facial erythema most commonly associated with embarrassment. It is generally considered to be physiological, albeit disliked by many easy blushers. Medically, a flush is considered to be a more marked blush and is often associated with a hot feeling, perspiration and pilo-erection. Occasionally the hot sensation may occur without the facial reddening.

Flushing and blushing are produced by transient vasodilatation. This can be caused by a variety of emotional, autonomic or endocrine factors or by the direct action of vasoactive drugs on the skin vasculature. Long-term flushing may be complicated by vascular damage with persistent vasodilatation and telangiectasia. Despite much research, the physiological mechanism is still poorly understood. A classification of the various causes, based on the distribution, is provided in Table 2.

Flushing is a relatively common complaint. Menopausal flushing is almost universal. In other people it is most commonly due to rosacea and patients will also have erythema, telangiectases, papules and pustules. Fevers from chronic relapsing infections are not always obvious and flushing may be the presenting symptom. Drugs are usually obvious as a cause because of the chronological association. All other causes are relatively rare. While many people associate phaeochromocytoma with flushing, this only occurs with the rare metastatic form that produces adrenaline rather than noradrenaline.

Management includes examination and investigations to identify the cause. Any suspected drug should be ceased. Despite exhaustive investigations, a number of cases remain idiopathic. Therapy is often unsatisfactory. As the natural history of flushing is for it to be episodic, it generally requires 4 to 6 weeks to adequately assess a trial of treatment. If there is an obvious precipitant such as alcohol consumption, hot drinks, spicy foods, sunlight or heat exposure, then it should be avoided. If the cause is considered to be rosacea, give a trial of antibiotics for 4 to 6 weeks, see Rosacea. In relevant females, even in the absence of biochemical evidence of impending menopause, consider hormone replacement therapy (see Ovarian replacement therapy).

Other treatments that have been effective in some cases include

aspirin 300 to 600mg orally, daily.

 

While aspirin may precipitate flushing in some people, it alleviates it in others. The presumed mechanism is inhibition of prostaglandins. While antihistamines are more likely to be effective in cases of urticaria pigmentosa, they may also be tried in flushing for 4 to 6 weeks. Use

dexchlorpheniramine 6mg OR loratadine 10mg orally daily.

 

Clonidine is effective in some cases. Use

clonidine 25 to 50 microgram orally, twice daily.

 

If the above measures are ineffective and the symptoms are sufficiently troublesome, vascular laser therapy of the telangiectases and erythema can be considered. While this treatment is not supported by clinical trial data, it is anecdotally effective in cases characterised by persistent erythema.

 

Type	Cause
facial	emotional, rosacea, idiopathic, nerve trauma (auriculotemporal syndrome, ciliary neuralgia, Riley Day syndrome)
acral	post-Raynaud’s attacks, erythromelalgia
dermographism	-
generalised	emotional, menopausal, febrile, drugs (amyl nitrite, nicotinic acid, nitrates, calcium channel blockers, other vasodilators, aspirin, chlorpropamide, disulfiram, opiates and other histamine-releasing agents), alcohol, food, carcinoid syndrome (metastatic), urticaria pigmentosa

Granuloma annulare

 

Granuloma annulare is a relatively common annular dermal granulomatous condition. It particularly affects the hands, on the dorsal surface or the digits, the dorsal surface of the feet and the extensor surface of the elbows. Histologically, the classical appearance is that of a palisading, histiocytic granuloma with the central portion involving damage to collagen, which is incomplete so that no scarring results. The natural history of the condition is one of spontaneous improvement but with peripheral extension. It may exist for months or years. A rarer, disseminated small papular form, particularly involving the trunk, may be associated with diabetes mellitus.

For most lesions, no treatment is necessary as spontaneous resolution is expected. However, treatment may be required because of the appearance, tenderness of the area or interference with normal function, eg on a finger.

Initial therapy consists of

a potent topical corticosteroid, with or without occlusion, applied for a minimum of 4 to 6 weeks.

 

If this is not effective, use

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, injected into the extending outer margin.

 

This may be repeated at 6-weekly intervals if effective. Referral is recommended for more severe and generalised involvement, for consideration of treatment with dapsone, prednisolone or phototherapy.

 

Hidradenitis suppurativa

 

Hidradenitis suppurativa is a relatively common and often misdiagnosed condition of the skin characterised by boils, pimples and comedones in the axilla, groin and submammary areas. It is also known as apocrine acne, as these are the sites of apocrine glands. The lesions often heal with scarring, which may be pitted and cribriform. It may occur alone or in association with severe cystic acne of the trunk, pilonidal sinus and dissecting cellulitis of the scalp, which are all part of the follicular occlusion tetrad. Dissecting cellulitis of the scalp is a severe folliculitis rather than a true bacterial cellulitis. Hidradenitis suppurativa is very commonly associated with obesity, and may be seen in women along with other features of androgen excess.

The aim of treatment is to provide first aid for the boils as they develop and to institute prophylaxis to guard against the development of new lesions. There is considerable person-to-person variation in the severity and frequency of the development of the boils, which will determine the need for prophylaxis.

First aid for the boils consists of

incision and drainage

AND

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, injected intralesionally

AND

a short course of oral antibiotics as indicated on sensitivity testing (see boils and carbuncles).

 

Antibiotic prophylaxis is modelled on the principles of acne therapy. Antibiotic resistance does, however, seem to be a problem and antibiotics are generally rotated every 4 to 6 months to prevent the emergence of resistance. The antibiotics that have been shown to be effective include

minocycline 50 to 100mg OR cotrimoxazole 80/400mg OR metronidazole 400mg OR erythromycin 500mg OR tetracycline 500mg OR cephalexin 500mg OR clindamycin 150mg orally, 12-hourly.

 

Other therapies that can be used for resistant cases include

cyproterone acetate 50 to 100mg OR spironolactone 100 to 200mg orally, daily for 10 days each month for females only

OR

isotretinoin (specialist referral is required).

 

If other treatments are unsuccessful, wide surgical excision or liposuction, which disrupts the glands, may be considered.

 

Lichen planus

 

Lichen planus is an idiopathic inflammatory condition. It may affect the skin, hair, nails and oral and genital mucosae. Alopecia occurs if the scalp is involved, and nail damage and destruction are seen when the nail matrix is affected. Occasionally lichen planus can be triggered by drug ingestion or hepatitis C infection.

Characteristically, the skin eruption consists of itchy, purple, polygonal, flat-topped papules that contain Wickham’s striae. These lacy white lines arranged in a reticular pattern are also seen on mucosal surfaces. Hypertrophic lesions may appear on the lower legs and tend to persist indefinitely.

A lichen planus-like drug eruption may also be produced by a variety of medications, particularly antihypertensive and antimalarial agents, see Lichenoid eruptions. This rash can mimic lichen planus clinically and histologically. Without treatment, the skin eruption usually resolves spontaneously over 6 to 9 months. A small proportion may persist indefinitely. Oral lesions and genital mucosal lesions have a tendency to be persistent. Nail and hair involvement may damage the stem cells and lead to permanent atrophy and destruction of the nails, see Nail disorders and a scarring alopecia of the scalp, see Hair disorders.

Skin lesions characteristically resolve with postinflammatory hyperpigmentation, which gradually fades over 3 to 6 months and does not require treatment. A number of clinical variants of lichen planus also exist, but these are beyond the scope of this text.

The aim of treatment is relief of symptoms while awaiting spontaneous resolution. It is important to consider the differential diagnosis of a drug-induced lichenoid eruption and withdraw any putative causative agent.

First-line therapy consists of

a very potent topical corticosteroid cream, applied to the affected areas twice daily

OR

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, 0.1mL intralesionally.

 

Intralesional corticosteroids are most suitable for hypertrophic variants of lichen planus. If this treatment is not successful, use

prednisolone 25mg orally, daily and weaned over 4 to 6 weeks.

 

If there is no response to prednisolone, alternative treatments are psoralen and ultraviolet A (PUVA) photochemotherapy, 3 treatments per week for 6 to 8 weeks, see Points on phototherapy, or acitretin [Note]. A variety of other medications, including griseofulvin, dapsone, antimalarial agents and cyclosporin, may also be effective in recalcitrant cases.

 

Related topics:

Lichenoid eruptions Oral lichen planus Lichen sclerosus of the genital area Corticosteroids - Getting to know your drugs Points on phototherapy

 

[Note]

Acitretin is teratogenic and pregnancy should be avoided during its use and for 2 years following cessation of therapy. In Australia, state laws require prescription of acitretin by a dermatologist.

Lymphoedema

Lymphoedema is due to lymphatic vessel obstruction, destruction or agenesis. Distal to the obstruction, lymph accumulates in the tissues, producing swelling and ultimately skin fibrosis. The combination of swelling and fibrosis produces nonpitting oedema. Impairment of the lymphatic circulation also interferes with the skin immune system and predisposes the affected area to bacterial cellulitis.

Lymphoedema may be primary or secondary. Primary lymphoedema (or Milroy’s disease) is commonly familial and three subtypes based on age of onset have been delineated: congenital (at birth), praecox (teens or early twenties) and tarda (after the age of 35).

Secondary lymphoedema may be due to proximal obstruction or removal of lymph vessels, or destruction of distal vessels. Proximal obstruction may be due to a space-occupying lesion or surgical removal of lymph nodes. Distal destruction may be due to recurrent cellulitis or erysipelas, fibrosis associated with chronic venous stasis, or neoplastic infiltration of the vessels as seen in Kaposi’s sarcoma. Elastolytic enzymes can be produced by bacteria, and recurrent episodes of bacterial infection may ultimately lead to lymphoedema.

Lymphoedema of the legs is almost invariably accompanied by some degree of pitting due to venous stasis. The aim of treatment is to alleviate limb soreness and numbness, minimise fibrosis, prevent hypertrophic epidermal changes (mossy foot), prevent leg ulceration, prevent cellulitis and erysipelas, and encourage patient mobility. Any associated venous oedema should be treated first.

Cellulitis and erysipelas generally require a portal of entry into the skin. This may be an abrasion or even interdigital tinea pedis. Even minor abrasions and tinea infections require aggressive treatments. Patients prone to recurrent episodes of cellulitis may benefit from prophylactic phenoxymethylpenicillin. First-line therapy consists of massage, compression bandaging, Unna’s boot, elastic hosiery and elevation. It is usually very difficult for patients to comply with this treatment and a lot of encouragement is required. For this reason, specialist lymphoedema clinics exist in most states and all patients should be referred to these clinics.

Milia

These small subepidermal keratin cysts may occur at any age, but particularly follow superficial damage to the skin below the dermo-epidermal junction, eg with blisters or abrasive injuries involving this level, or after sunburn. They are thought to originate from the duct lining of sweat and sebaceous glands. Spontaneous disappearance may occur, particularly in children. Incision of the epidermis with a cutting edge needle or sharp pointed scalpel and squeezing out the contents is all that is required for treatment of each individual lesion.

Necrobiosis lipoidica diabeticorum

This characteristic eruption of diabetes consists of expanding red-brown plaques on the shins, which eventually may become atrophic in the centre and develop ulceration. Up to 70% of patients with this condition will have overt insulin or noninsulin dependent diabetes mellitus. Initial lesions are red, with the centre becoming brownish-yellow with obvious telangiectases and eventually thinning of the epidermis and dermis, leading to an atrophic change which is likely to form indolent, slow-healing ulcers.

Histologically, there is focal loss of collagen in the lower dermis, with a granulomatous infiltrate and evidence of endothelial proliferation and occlusion of the lumina of arterioles and venules. Differential diagnosis includes sarcoid, granuloma annulare and diabetic dermopathy, which does not develop atrophic changes.

Treatment involves protection from trauma to prevent breakdown, together with

a very potent topical corticosteroid under occlusion (see Points on use of modified dressings) for early lesions

AND/OR

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, injected intralesionally, particularly around the advancing border.

 

In more severe cases clofazimine, dapsone, pentoxifylline and skin grafting have given varying results.

Palmoplantar keratoderma

 

Keratoderma refers to thickening of the skin. Keratoderma of the palms and soles may be diffuse or punctate, characterised by multiple wart-like areas. The cause may be hereditary or acquired. Hereditary cases may occur as a solitary abnormality with no or few associated problems, or it can be part of a syndrome. The causes of acquired diffuse keratoderma include keratoderma climactericum, tinea, dermatitis, psoriasis, lichen planus, cutaneous T-cell lymphoma, Reiter’s syndrome, acanthosis nigricans, pityriasis rubra pilaris and myxoedema. The causes of acquired punctate keratoderma include callosities, warts, lichen planus, arsenic, Reiter’s syndrome, psoriasis and infections such as yaws.

Most cases are acquired. All longstanding cases should be referred to a dermatologist for assessment. The assistance of a clinical geneticist may be required. The genes for many of the inherited conditions have now been identified and prenatal testing is available for some.

Acquired keratoderma will usually respond to treatment of the cause. Keratoderma climactericum is named because it commonly affects women in their forties and fifties around the time of the climacteric, although no hormonal basis has been identified. It presents with thickening of the heels, which are prone to fissures. Palliation is required for the inherited keratodermas. Apart from treatment of any known cause, initial treatment consists of keratolytic creams, including

urea 10 to 30% cream OR salicylic acid 3 to 50% cream or ointment OR alpha-hydroxy acid 2 to 20% cream.

 

If there is no response and the condition is severely disabling, treatment consists of oral therapy with acitretin. Treatment with acitretin is suppressive and the condition returns on cessation of therapy. Many patients are intolerant of the adverse effects.

Fissures are a common complication and may be treated with an occlusive cream or dressing such as

white soft paraffin OR flexible collodion OR hydrocolloid dressings.

 

Superglue and nail polish have also been used.

Perniosis

Chilblains or perniosis are localised inflammatory lesions that are caused by continued exposure to cold above the freezing point. Dampness or wind can increase the cold conductivity. Chilblains develop acutely as burning erythematous or purplish swellings, most frequently on toes and fingers and less frequently on the heels, nose and ears. They resolve in 1 to 3 weeks. Histological changes vary from a perivascular lymphocytic infiltrate to a lymphocytic vasculitis.

Prevention is by creation of a more favourable environment and the wearing of warm but not tight clothing. For treatment, use

a potent to very potent topical corticosteroid.

 

For severe and recurrent disease, preventative therapy has been used

nifedipine 20mg orally, 3 times daily OR PUVA therapy (see Points on phototherapy).

 

Once lesions occur, rest and warmth of the affected part are the mainstay of therapy.

Pityriasis rosea

Pityriasis rosea is a relatively common, self-limiting inflammatory skin condition that characteristically affects young adults. The cause is thought to be a virus (possibly human herpesvirus 7). The eruption begins with a herald patch that may be mistaken for ringworm. This is followed about 2 weeks later by the development of multiple, scaly, salmon-coloured macules, each about 1 to 2cm in size and oval in shape. The macules are confined to the trunk and upper limbs and are arranged along the skin creases to create an appearance reminiscent of a Christmas tree. Itch is variable. The rash disappears spontaneously, usually within 6 to 8 weeks.

The aim of treatment is palliation of any associated itch while awaiting spontaneous resolution. In the absence of itch, reassurance may suffice. To relieve itch, first-line therapy consists of topical antipruritic agents such as

calamine lotion OR menthol 1% in aqueous cream.

 

For more severe itch, use

a moderately potent topical corticosteroid cream, applied 2 to 3 times daily.

 

Ultraviolet B (UVB) phototherapy can be used to relieve itch and may hasten resolution of the rash.

Pityriasis rubra pilaris

 

This is an erythematous scaling disorder which, in its most common form, may be mistaken for severe and widespread psoriasis. Initial lesions are characteristically keratotic follicular papules but, in the most common form of the disease, there is continued extension cephalocaudally with rapid coalescence to form erythematous scaling plaques covering most of the body and a characteristic yellowish palmoplantar keratoderma. Although spontaneous recovery is the rule, this often takes longer than 12 months and is not greatly altered by treatment. Diagnosis is made on a combination of clinical features and biopsy, but differentiation from psoriasis and other forms of erythroderma may sometimes be difficult.

Specialist referral is necessary for consideration of systemic treatment with acitretin [Note] or methotrexate.

[Note]

Acitretin is teratogenic and pregnancy should be avoided during its use and for 2 years following cessation of therapy. In Australia, state laws require prescription of acitretin by a dermatologist.

Polymorphic light eruption

Polymorphic light eruption is a relatively common idiopathic disorder characterised clinically by an intermittent, delayed and transient abnormal cutaneous reaction to ultraviolet (UV) light exposure. The reaction consists of nonscarring pruritic erythematous papules, vesicles or plaques on light-exposed skin, particularly the forearms and the V of the neck. The face is more likely to be involved in patients where previous ‘hardening’ by regular exposure is low, eg countries in higher latitudes. The reaction is least common in equatorial areas where the UV light intensity remains fairly constant for a full year. Lesions usually occur within hours of exposure and last 1 to 7 days. Histologically, the characteristic appearances are those of a perivascular dermal lymphocytic infiltration. Differential diagnosis includes subacute cutaneous lupus and drug eruption.

For mild disease most patients learn to avoid periods of high UV intensity or cover up with clothing. Sunscreens with good ultraviolet A (UVA) protection are required because this is the usual action spectrum for the disease, eg titanium dioxide sunscreen agents.

For symptomatic relief of the rash, particularly if a vesicular element is present, use

a potent topical corticosteroid.

 

If these measures prove ineffective, specialist referral is warranted for consideration of PUVA or narrowband UVB therapy, which are used to ‘harden’ the skin to UV light. Alternative therapies used include hydroxychloroquine, thalidomide and beta-carotene.

 

Pretibial myxoedema

 

Pretibial myxoedema is a feature of Graves’ disease and may be associated with thyrotoxicosis and exophthalmos. It is characterised by either diffuse or nodular swelling of the front of the shins. Histologically, there is an accumulation of mucin in the dermis.

The condition is usually asymptomatic, in which case no treatment is required. If treatment is required, use

a very potent topical corticosteroid, applied to the affected area, with or without occlusion, once or twice daily for 4 to 6 weeks to judge efficacy

OR

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, injected intralesionally, determined by the lesion size.

 

Treatment may need to be repeated at monthly intervals. Compression stockings may reduce any swelling and will correct any associated venous insufficiency.

 

Pyogenic granuloma

 

Pyogenic granuloma is a rapidly developing vascular nodule, usually at the site of a recent injury, and is composed of proliferating capillaries in a loose stroma. It is seen most commonly in children and young adults, and frequently bleeds easily. Differential diagnosis includes keratoacanthoma, inflamed seborrhoeic keratosis, amelanotic melanoma, molluscum contagiosum, Kaposi’s sarcoma and metastatic carcinoma. All of these will be excluded by the histology of the removed lesion.

Excision biopsy with a narrow but deep ellipse of skin beneath the lesion is advisable where possible. However, narrow based lesions and those adjacent to nailfolds may be treated by curettage and cautery. Recurrence is more likely following the latter procedure.

Reiter's syndrome

 

It is a genetically determined immune response, affecting skin, eyes and joints, that usually develops several weeks after the infection of the gut or urinary tract with certain microorganisms. Clinically, balanitis, keratoderma blennorrhagicum and onychodystrophy are associated with conjunctivitis, mouth ulcers and acute oligoarthritis, primarily involving the knee and ankle, and inflammation of tendon and ligament insertions, particularly the Achilles tendon, dactylitis, urethritis or cervicitis.

Like other serum-negative spondyloarthropathies, it exhibits varying degrees of arthrocutaneous and ocular manifestations. It exhibits familial clustering, an inherited predisposition associated with the presence of major histocompatibility complex class I alleles, such as human leucocyte antigen B27. This leads to an abnormal cellular immune response centred on the CD8 T-cell, which is enhanced by the unbalanced CD8 population of advanced human immunodeficiency virus (HIV) infection.

The postdysenteric form of Reiter’s syndrome is usually associated with salmonella and shigella infections, whilst the posturethritic form is most commonly associated with chlamydia infections.

Keratoderma blennorrhagicum consists of red-brown papules, vesicles and pustules with central erosion on the soles, toes and palms. Circinate balanitis is found in one-third of patients with Reiter’s syndrome.

Skin changes can occur with or before the arthritis, but usually within 1 to 4 weeks of the initial infection. Diagnosis is difficult because of the lack of any one diagnostic test and the variable relationship of any of the diagnostic features to one another. The appearance of an eruption and arthritis resembling pustular psoriasis in a patient with HIV infection should arouse suspicion of Reiter’s syndrome.

Management of the acute mucocutaneous lesion usually involves moderately potent topical corticosteroids for the balanitis, and tar and topical corticosteroid preparations for the keratoderma. The skin lesions alone rarely justify systemic therapy; however, the severe extensive and chronic cutaneous reactions that are more commonly associated with HIV infection may warrant treatment, as for pustular psoriasis, with UVB, coal tar and acitretin administration.

For severe skin lesions where HIV infection is not present, methotrexate, PUVA or cyclosporin may also be considered.

[Note]

Acitretin is teratogenic and pregnancy should be avoided during its use and for 2 years following cessation of therapy. In Australia, state laws require prescription of acitretin by a dermatologist.

Sarcoidosis

 

Skin lesions of sarcoid occur in about 25% of patients and may be either specific or nonspecific. Specific lesions most commonly are yellowish-brown plaques or nodules found particularly on the face and extremities. Involvement of old scars with infiltrated plaques of sarcoid is quite characteristic. Rarer specific involvement, seen in lupus pernio, involves the presence of chronic violaceous indurated skin lesions on the nose, ears and lips. This is associated with more severe and established systemic involvement.

Nonspecific lesions of sarcoidosis include erythema nodosum, erythema multiforme, ichthyosis, alopecia and erythroderma. Erythema nodosum is by far the most common of these and is discussed in more detail here. Erythema nodosum in patients with sarcoid is particularly associated with hilar lymphadenopathy and pulmonary involvement. Diagnosis of specific involvement is confirmed by the appearance of typical sarcoid granulomas in a skin biopsy specimen. Differential diagnosis includes granuloma annulare, necrobiosis lipoidica and granulomatous infections of the skin, eg tuberculoid leprosy and other mycobacterial infections.

Management of specific skin lesions involves exclusion of systemic involvement by clinical examination, chest X-ray, pulmonary function tests and serum angiotensin converting enzyme estimation. Local therapy consists of

triamcinolone acetonide 10mg/mL OR betamethasone acetate/sodium phosphate 5.7mg/mL, injected into the individual plaques, using up to 1mL in each treatment session.

Spider naevi

 

The central portion of the spider is an arteriole and the peripheral branches emanate from this. They are common in childhood and occasionally are associated with liver disease. Destruction of the central vessel with cautery or laser is usually effective. In the case of recurrence, a small, deep excision may be necessary.

Sweet's syndrome

 

It is also known as acute febrile neutrophilic dermatosis. This condition involves the rapid appearance of painful oedematous, erythematous plaques on the face, neck and limbs, sometimes but not always accompanied by fever. The plaques may have a vesicular or pustular appearance to them.

Histologically, there is a striking infiltration of mature polymorphs in the dermis with some fragmentation and quite pronounced upper dermal oedema. There is no convincing evidence of vasculitis. The presumed aetiology is a hypersensitivity reaction to a possible, but as yet undefined, bacterial or viral antigen.

The condition may be self-limiting or recurrent, but usually responds very dramatically to systemic corticosteroid therapy. Persistent or recurrent disease is particularly associated with myeloid dysplasias, including myeloid leukaemia. It has also been reported in association with administration of granulocyte colony stimulating factor, indicating that altered granulocyte function may be important.

Diagnosis is a combination of characteristic histology, clinical picture, raised neutrophil leukocyte count and erythrocyte sedimentation rate, and positive antineutrophil cytoplasmic antibody.

Erythema multiforme, erythema nodosum, cutaneous vasculitis, drug eruption and pyoderma gangrenosum should be excluded. This is best done by a skin biopsy.

First-line therapy is with

prednisolone 25 to 50mg orally, daily for 1 to 2 weeks then taper the dose to 10mg orally, daily by 4 to 6 weeks.

 

Second-line therapy is with

colchicine 1.5mg orally, daily for 7 days, reducing to 0.5mg orally, daily for 3 weeks.

 

Other treatments that have proved effective in some patients include indomethacin, minocycline, potassium iodide, clofazimine and dapsone.

Xanthoma

 

Xanthoma represents abnormal accumulation of lipid in the dermis and although there are several different forms, all have a characteristic yellow component. All forms of xanthoma may be associated with disorders of lipid metabolism although occasionally they may occur in association with localised inflammatory disease, neoplastic disease or lymphoedema. Exclusion of a defect of lipid metabolism is always warranted. Many xanthomas will respond well to dietary control and/or drug treatment of their lipid abnormality. Xanthelasma palpebrum often warrants further therapy because of its unattractive cosmetic appearance and cautery, cryotherapy, treatment with trichloracetic acid 40% and excision are all used for this.

 

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