Paediatrics: Pigmentation disorders

Pigmentation disorders

Hyperpigmented lesions

Generalized hyperpigmentation (hypermelanosis)

Causes

•   Racial.

•   Sun.

•   ACTH (e.g. hypoadrenalism).

•   Chronic renal failure (i melanocyte-stimulating hormone (MSH)).

•   Malabsorption.

•   Drug reaction.

Localized hyperpigmentation (hypermelanosis)

Causes

•   Pigmented naevi (see bullet points in Pigmented naevi, following).

•   Freckles.

•   Lentigines.

•   Café au lait macules.

•   Neurofibromatosis (before puberty 6 café au lait macules >0.5cm diameter, axillary freckles).

·  Viral warts.

•   Polyostotic fibrous dysplasia (McAS).

•   Peutz–Jegher’s syndrome (perioral brown macules); post-inflammatory skin disease or trauma.

Pigmented naevi

•   Melanocytic naevus (mole): developmental anomaly of melanocyte migration. May be brown, black, or pink, macular, papular, hyperkeratotic or smooth, hairy or hairless. Almost universal, commonly on face, neck, or back, appearing after birth throughout childhood, particularly at puberty. Treatment usually not required. Surgical removal appropriate for cosmetic reasons, recurrent trauma (e.g. from bra straps), or malignant change (rare in childhood). If congenital, can be extensive—refer to dermatologist/plastic surgeon for treatment and follow-up.

•   Halo naevus: area of depigmentation around mole due to production of autoimmune antibodies to melanocytes. Usually reassurance alone is needed, but if irregular depigmentation or irregular mole is present refer to a dermatologist.

•   Mongolian blue spot: macular blue-black lesion present at birth, common in dark-skinned races, particularly over sacrum, buttocks, back, and shoulders. Most fade spontaneously by age 10yrs.

•   Spindle-cell naevus: benign melanocyte tumour. Red-brown dome-shaped nodule. Treated by simple excision.

Malignant melanoma: rare in childhood. Risk increases with increased sun exposure. Occurs in older children, those with giant congenital pigmented naevi, immunosuppressed, previous chemotherapy, albinism, xeroderma pigmentosum. Change in mole colour, shape, size (unless in proportion to child’s growth), ulceration, itch, or haemorrhage requires urgent specialist excision biopsy and histology.

Hypopigmented lesions

Generalized hypomelanosis

Causes

• Hypopituitarism (d ACTH and ‘fall’ MSH).

• Oculocutaneous albinism.

• Protein-energy malnutrition.

• Poorly controlled phenylketonuria (phenylalanine acts as a competitive inhibitor of tyrosinases).

Oculocutaneous albinism

An autosomal recessive disorder of melanin synthesis. It presents with hypopigmented skin, blonde hair, pink irises, photophobia, reduced visual acuity, nystagmus.

Treatment 

Restrict sunlight exposure, e.g. protective high-level sunscreen; ophthalmology referral.

Localized hypomelanosis

• Vitiligo: common autoimmune disease (anti-melanocyte antibodies present) resulting in sharply demarcated, often symmetrical white patches. Treatment Reassurance. If severe—topical steroids; cosmetics; sun protection; phototherapy. Lesions usually persist.

• Pityriasis versicolor.

• Pityriasis alba: common in prepubertal children. Represents low grade eczema with post-inflammatory hypopigmentation. Hypopigmented 1–2cm macules +/– fine scale on face or upper body. Treatment— topical hydrocortisone 1%, frequent moisturizing. Resolves in 2–3wks.

• Post-inflammatory depigmentation.

Tuberous sclerosis ‘ash leaf’ macules: small oval hypopigmented macules that are more easily seen under Wood’s light examination.