Incontinentia pigmenti

Incontinentia pigmenti

This rare condition is an X-linked dominant disorder, usually lethal before birth in males. The gene for fam-ilial cases has been mapped to Xq28 and that for the more severe sporadic cases to Xp11. The bizarre pat-terning of the skin is caused by random X-inactivation (Lyonization). The lines of affected and normal skin represent clones of cells in which either the abnormal or normal X chromosome is active.

Clinical features

There are three stages in the evolution of the skin signs.

1  Vesicular. Linear groups of blisters occur more onthe limbs than trunk.

2 Warty. After a few weeks the blisters dry up and thepredominant lesions are papules with a verrucous hyperkeratotic surface.

3 Pigmented. A whorled or ‘splashed’ macular pig-mentation, ranging from slate-grey to brown, replaces the warty lesions. Its bizarre patterning is a strong diagnostic pointer.

Occasionally, the vesicular and warty stages occur in utero; warty or pigmented lesions may therefore bethe first signs of the condition. There is also a variant in which pale rather than dark whorls and streaks are seen.

Associated abnormalities are common. One-quarter of patients have defects of their central nervous system, most commonly mental retardation, epilepsy or micro-cephaly. Skull and palatal abnormalities may also be found. Delayed dentition, and even a total absence of teeth, are recognized features. The incisors may be cone- or peg-shaped. Ocular defects occur in one-third of patients, the most common being strabismus, cataract and optic atrophy.

Differential diagnosis

Diagnosis is usually made in infancy when bullous lesions predominate so the differential diagnosis in-cludes bullous impetigo, candidiasis, and the rarer linear immunoglobulin A (IgA) bullous disease of childhood  and epidermolysis bul-losa.

Investigations

There is frequently an eosinophilia in the blood. Biopsy of an intact blister reveals an intraepidermal vesicle filled with eosinophils.

Management

This is symptomatic and includes measures to combat bacterial and candidal infection during the vesicular phase. Family counselling should be offered.