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Pigmentation disorders

Pigmentation disorders

Hypermelanosis and hypomelanosis are due, respectively, to increased and decreased amounts of melanin in the skin. They may be generalised or localised.

Common causes of localised hypomelanosis are:

           vitiligo

           postinflammatory hypomelanosis

           pityriasis alba

           pityriasis versicolor

           idiopathic guttate hypomelanosis

           halo naevus.

Common causes of localised hypermelanosis are:

           chloasma

           postinflammatory hyperpigmentation

           poikiloderma of Civatte.

Apart from hypermelanosis, increased pigmentation of the skin can be due to haemosiderin, drugs and other causes. A complete discussion of this subject is beyond the scope of these Guidelines.

Vitiligo

Vitiligo is a common disorder, affecting 0.5 to 1% of the world’s population. It is of greater cosmetic significance in pigmented races. It is strongly familial. The aetiology of vitiligo is unknown, but it may be associated with other autoimmune disorders in which organ specific autoantibodies to thyroid, gastric parietal cells and adrenal tissue are present. One-half of all vitiligo cases present before the age of 20. Body sites most commonly affected are the face, hands, ankles, flexures, nipples and genitals. Pigment loss may be partial or complete. Borders of the lesions may be hyperpigmented and hairs in the area may also lose their pigment.

The prognosis of this condition is poor. Patients require emotional support, cosmetic camouflage and sun protection, and should seek dermatological assessment. Spontaneous repigmentation, either partial or complete, occurs in 10 to 20% of cases. The disorder responds erratically to therapy. Therapies include phototherapy and topical corticosteroids.

Light therapy, either alone or with the photosensitising psoralen family of drugs, is the mainstay of therapy. Patients may require more than 50 treatments before results are seen. The first sign of repigmentation is a follicular pattern. Response to therapy may be incomplete, even after many months. The areas of hypopigmentation may extend despite therapy. Recent studies on the use of narrowband ultraviolet B (311nm) light alone have produced encouraging results.

Psoralen-ultraviolet A (PUVA) - Exposure to metered doses of ultraviolet A (UVA) radiation (320 to 380nm) 2 hours after oral administration of methoxsalen 0.6mg/kg may be helpful, see PUVA therapy. Adverse effects include nausea from the psoralen, itch and burning of the hypopigmented areas, and, after many cumulative doses, freckling of uninvolved skin, skin atrophy and the possible development of squamous cell carcinoma.

Where vitiligo is very localised, the topical application of weak psoralen (methoxsalen) is justified and may produce rapid repigmentation. This is a somewhat hazardous technique, as the therapeutic index of the topical psoralen is low, and burns are common.

Very potent topical corticosteroids, can bring about some repigmentation in patches of vitiligo, but generally cause skin atrophy and should not be used on facial lesions. Use

betamethasone dipropionate 0.05% (optimised vehicle) cream applied twice daily for 2 to 3 months.

Postinflammatory hypomelanosis

Some inflammatory dermatoses leave areas of hypopigmentation as they resolve. An increased epidermoid mitotic rate interferes with transfer of melanosomes to keratinocytes. This is seen especially in psoriasis and eczema, but is common with many dermatoses in patients with olive and dark skin, and is especially seen after cryotherapy. Pigmentation returns to normal often weeks or months after some exposure to sunshine.

Pityriasis alba

This superficial dermatitis commonly presents with round, ill-defined pale or pink areas, 0.5 to 2cm in diameter, with a fine scale, especially on the face and upper arms of olive-skinned children. The disorder is not confined to atopic patients. Most cases are persistent, but improve in adolescence. It does not respond well to treatment. Avoidance of soap contact with the areas is recommended, with application of emollient or a weak topical corticosteroid.

Use

glycerol (glycerin) 10% in sorbolene cream OR hydrocortisone 1% ointment applied daily.

Pityriasis versicolor

This chronic, superficial yeast infection of the skin can present with areas of hyperpigmentation or hypopigmentation.

It is caused by the budding yeast Malassezia furfur, which is the mycelial phase of the yeast Pityrosporum orbiculare, which is part of the normal skin flora.

The hypopigmentation is due to tyrosinase inhibition by dicarboxylic acids produced by the pityrosporum, with consequent suppression of melanin production. Abnormal melanosomes may also be produced by a disruption in this pathway, accounting for the hyperpigmentation seen in other patients with this disorder.

Pityriasis versicolor is seen in young patients, with a peak incidence between 20 and 30 years of age. It is common in tropical climates. The sex incidence is equal and there may be a genetic predisposition to develop this reaction to normal skin flora.

Patients present with well demarcated pale or tan-coloured macules, some of which may coalesce, with fine scale, usually on the upper trunk alone. However, the condition may involve the whole trunk, the upper arms and the neck. There may be a slight itch.

Skin scrapings reveal spherical budding yeasts and coarse mycelia on microscopy.

Topical therapy is with

ketoconazole 2% shampoo applied daily for 10 minutes and washed off, for 10 days

OR

selenium sulfide 2.5% shampoo applied daily for 10 minutes for 7 days

OR

sodium thiosulfate 20% solution applied twice daily for 2 weeks.

If the disease is localised to a small area it is reasonable to use

imidazole cream or lotion topically, twice daily for 10 days.

In unresponsive cases, use systemic therapy with

ketoconazole 200mg orally, daily for 10 days OR itraconazole 200mg orally, daily for 5 days.

The hypopigmentation may persist for some months until adequate sun exposure repigments the areas of pallor. It can be recurrent in some individuals and repeated courses of treatment may be necessary. Alternatively, intermittent doses of systemic medication (pulse therapy) can be used to suppress the growth of the yeast. Use

ketoconazole 400mg OR itraconazole 200mg orally, once every 30 to 90 days.

Idiopathic guttate hypomelanosis

This common disorder is seen in middle age, more often in women than men. Multiple small (2 to 5mm diameter) hypopigmented macules appear, especially on the arms and legs. The condition probably represents areas of melanocyte malfunction in areas of chronic sun damage in predisposed patients. Very superficial cryotherapy has been reported to encourage repigmentation in these lesions.

 Halo naevus

Depigmented areas may appear around melanocytic naevi. These lesions are common, sometimes multiple, and are seen in all ages, most often in adolescents. The naevus regresses over months or years, the halo eventually repigments and the skin returns to normal. No treatment is required, apart from protection against sunburn.

Chloasma (melasma)

This can occur in men but is seen predominantly in women. It is most common during pregnancy, but may occur at any time during a female’s reproductive years. Chloasma is more common in patients with olive complexions. Sites of predilection are the upper lip, malar area, and forehead. The areas are light brown and are usually symmetrical.

The putative pathogenesis of chloasma is that the facial skin contains oestrogen receptors and when activated, these receptors somehow enhance the ability of that skin to tan in response to sunlight. This is certainly an over-simplification, as histologically there are two subgroups of chloasma – those with increased epidermal pigmentation and those with increased pigmentation in the dermis (pigmentary incontinence). The mechanism producing dermal chloasma is not known. Drugs may also be a cause, eg oral contraceptives, phenytoin and others.

All the treatments are very slow-acting and patients need to be warned that minimal change is expected within 3 to 6 months and treatment often needs to be continued beyond 12 months. In addition, relapse on cessation of the treatment is common.

Sun protection is paramount. Avoidance of sunshine, wearing of hats and the regular application of a high efficiency sunblock, preferably one containing microfined titanium dioxide, will all help to prevent further lesions and fade older ones, although fading may be very slow.

In minor cases, reassurance may be all that is needed. Laser therapy is often disappointing. Facial peels with glycolic acid are suitable treatments, but caution should be exercised.

Topical therapy with depigmenting agents may be used, eg

hydroquinone 2 to 5% cream OR tretinoin 0.05% cream OR azelaic acid 20% cream OR glycolic acid 12% cream or lotion.

Some creams, eg hydroquinone 5%, may need to be extemporaneously compounded for individual patients.

Resistant cases may be treated by a suitably experienced doctor, using facial peels with glycolic acid 20 to 70%.

 Postinflammatory hyperpigmentation

This occurs especially in dark-skinned patients and can occur after any acute or chronic inflammation. The inflammation that causes this involves basal layer disruption and results in melanin being localised in upper dermal melanophages for weeks or months, producing the clinical picture of hypermelanosis.

Dermatoses commonly causing this in olive-skinned and dark-skinned patients include acne vulgaris, atopic dermatitis, acute contact dermatitis, lichen planus, psoriasis, drug eruptions and lupus erythematosus.

The pigmentation usually fades in time, varying from weeks to months. Depigmentary creams are not helpful and laser therapy is not indicated.

 Poikiloderma of civatte

This picture of hyperpigmentation, telangiectasia and atrophy is very common in sunny countries and occurs in women over 40 years of age. It affects the sides of the neck and the V of the neck especially, but spares the shaded area beneath the chin.

The cause in unknown, but sun damage and the spraying of perfumes containing photodynamic substances onto the neck are possible causes.

Sunblocking creams, see Sunscreens, must be used assiduously. Tretinoin and glycolic acid creams help, but progress is slow. Use

maximum protection sunscreen with titanium dioxide applied each morning

AND

tretinoin 0.05% cream OR glycolic acid 12% cream applied nightly.

Tretinoin and glycolic acid preparations may cause irritation.

Large spot size lasers such as the pulsed dye laser at 585nm and the variable pulse width 532nm lasers have been shown to improve the diffuse telangiectasia. Response to laser therapy is highly variable and is often unsatisfactory because of the large area that needs to be treated. Several treatments are needed to effect significant improvement.

 Pregnancy rashes

Rashes in pregnancy are divided into two groups. The first group consists of rashes that are only seen in pregnant women, and includes conditions such as pruritic urticarial papules and plaques of pregnancy (PUPPP), pemphigoid gestationis (previously named herpes gestationis and bullous dermatosis of pregnancy), pruritic folliculitis of pregnancy, pruritus of pregnancy, prurigo of pregnancy and erythema nodosum of pregnancy. All of these conditions are uncommon or rare. The second group consists of pre-existing conditions that are worsened by pregnancy, eg atopic dermatitis, rosacea, psoriasis, acne, pityrosporum folliculitis, herpes simplex, vulvovaginal candidiasis and lupus erythematosus.

Treatment of all skin conditions in pregnancy is difficult. There is often a poor response to therapy, which in itself is limited. In most cases the condition is unable to be effectively treated until the pregnancy is over. Use of medication to treat benign skin conditions in pregnancy should be limited to category A drugs, Australian Categorisation of Drugs in Pregnancy, see chapter on Drug use in pregnancy and breastfeeding.

This is the most common of the rashes specific to pregnancy, presenting in primigravidae towards the end of the third trimester, with itchy plaques and papules beginning on the abdomen and spreading to the rest of the trunk, arms and legs. The eruption clears promptly after delivery and does not recur in subsequent pregnancies.

The following treatment is recommended

a potent topical corticosteroid applied twice daily under wet dressings (see Points on use of modified dressings)

AND

hydroxyzine 25 to 50mg orally, 3 times daily.

In extreme cases where the patient is unable to sleep because of itching, prednisolone 25mg orally, daily may be used. Consultation with a dermatologist and obstetrician in this situation is recommended.

This is a rare, autoimmune condition in which a rash, which may initially resemble PUPPP, occurs initially in the second to third trimester (average time of onset is 21 weeks) and resolves postpartum. The rash tends to recur earlier in each subsequent pregnancy. Onset of the rash may sometimes be in the first week postpartum, and it may not clear for several weeks. The rash is unresponsive to topical corticosteroids and if left untreated may become vesicular or bullous. This eruption should be diagnosed by skin biopsy.

Treatment is with

prednisolone 0.5 to 1mg/kg orally, daily until eruptions and itching have resolved, then gradually withdrawn over 6 weeks.

Referral to a dermatologist is recommended.

This rare condition occurs in the second or third trimester. Very itchy follicular papules and pustules occur mainly on the upper body and arms. Swabs should be taken to rule out a Staphylococcus aureus infection; however, in this condition they are negative. Treatment with potent topical corticosteroids may be used but the response can be disappointing. The condition resolves after delivery.

Itch without an observable rash or skin disease may occur in pregnancy, usually in the third trimester. This may be idiopathic or due to pregnancy-associated cholestasis. In all cases, serum bile acids and liver function tests must be checked. Both will be elevated in cholestasis and this condition is usually managed with induction at or before 38 weeks, depending on severity, as continuation of the pregnancy beyond this time is harmful to the fetus. Both conditions may be very distressing to the patient; however, therapy is ineffective. The itching resolves promptly after delivery.

Erythema nodosum may occur in pregnancy, with no other identifiable cause. Other causes of this condition, such as bacterial and other infections, sarcoidosis, enteropathies, drugs and malignancies, should be ruled out. The condition is usually not disabling. No treatment other than bedrest is usually required. It resolves after delivery.

Atopic dermatitis – may be managed in the usual way, see General treatment of dermatitis. Topical corticosteroids are considered safe in pregnancy.

Psoriasis – topical therapy, including corticosteroids, dithranol and tars, see Topical therapy in management of psoriasis, and ultraviolet B therapy, see Phototherapy in management of psoriasis, may be used in pregnancy. Oral therapy is contraindicated.

Acne and rosacea – rarely, both conditions may be present in a very severe form in pregnancy. Treatment is limited to oral or topical erythromycin, the effect of which is often disappointing. Recovery after the birth of the baby may be delayed for weeks or months.

Herpes simplex – if present in a severe degree in pregnancy, aciclovir (category B3) may be used. Consultation with an infectious disease specialist is recommended.

Pityrosporum folliculitis and vulvovaginal candidiasis – topical nystatin and imidazole antifungals may be used in pregnancy. Oral therapy is contraindicated.

Lupus erythematosus and other autoimmune conditions – may flare in pregnancy, and may require treatment with oral prednisolone and azathioprine. Specialist consultation is recommended.

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