Albinism and Piebaldism

Synonyms

None.

Epidemiology

Albinism: 1 in 20 000 people; highly variable in different populations. (1 in 1 000 people in some genetically isolated communities).

Piebaldism: 1 in 40 000 Caucasians.

Definition

These genetic conditions cause partial or total depigmentation of the skin, hair or eyes.

Aetiology & Pathogenesis

Albinism: Usually autosomal recessive inheritance. Non-inflammatory disease is due to reduced or absent tyrosinase activity, causing reduced or absent melanin pigment, despite normal numbers of melanocytes (unlike vitiligo, where there are fewer melanocytes). This is due to interruption of the synthesis of melanin via enzyme malfunction or absence, as well as other, rarer, mechanisms.

Piebaldism: Usually autosomal dominant inheritance. Mutation in KIT proto-oncogene causing reduced melanocytes. Compare differences to chapter Vitiligo.

Signs & Symptoms

Albinism: apart from a tendency to sunburn, asymptomatic for the skin, except for potential cosmetic embarrassment. Ocular symptoms may include poor visual acuity, photophobia and nystagmus, as well as other features.

Piebaldism: same as for albinism, but no ocular features. The changes are present from birth, unlike vitiligo.

Localisation

Albinism: the absence of skin pigmentation is usually generalised, but more localised forms (i.e. periorificial) exist. In some subtypes, the scalp hair may be a yellow colour and the leg hairs dark.

Piebaldism: A characteristic white forelock of hair is almost always seen in the mid forehead. Depigmented skin is commonly patchy, with typical sites including mid extremities and central trunk.

Classification

Albinism: this is according to the particular defect in melanin synthesis resulting from mutations in the tyrosinase protein genes.

Piebaldism: no classification.

Laboratory & other workups

Differentiating different types of albinism is not usually of clinical relevance and such tests are not routinely available apart from in specialised centres. One particular test is to incubate a hair bulb with tyrosinase. This test may differentiate tyrosinase positive and negative forms of albinism.

Dermatopathology

This is not required and is not generally helpful, unless to exclude other conditions. Melanocytes present but disturbed function.

Course

The conditions are lifelong.

Complications

The most important cutaneous complication is of skin cancer. The risk of developing a skin cancer is greatly elevated as there is no natural sun protection in albinos. They are most prone to develop squamous cell carcinomas and this may occur at very young ages, particularly in those who live in tropical climates. Decreased quality of life can be observed in both albinism and piebaldism.

Diagnosis

The diagnoses are clinical.

Differential diagnosis

Vitiligo, post-inflammatory hypopigmentation, idiopathic guttate hypomelanosis, rare genetic syndromes eg Waardenburg syndrome.

Prevention & Therapy

Camouflage. No known effective treatments for the underlying problem. In piebaldism, hair colouring possible.

Limited surgical procedures (skin transplants) are performed in countries with darker skin.

Effective sun protection (high factor topical sunscreens and clothing, including hats) essential to avoid skin cancers. Ophthalmological review is mandatory in albinism and psychological support should be offered.

Special

In some cultures of the world, body parts from those suffering from albinism are thought to possess magical or medicinal powers. In those situations, albinos may be persecuted and require police protection. See ILDS website for more information.

6.3.5 Albinism and Piebaldism