X-linked recessive ichthyosis

X-linked recessive ichthyosis

Cause

This less common type of ichthyosis is inherited as an X-linked recessive trait and therefore, in its complete form, is seen only in males, although some female carriers show mild scaling. The condition affects about 1 in 6000 males in the UK and is associated with a deficiency of the enzyme steroid sulphatase, which hydrolyses cholesterol sulphate. The responsible gene has been localized to the terminal part of the X chro-mosome at Xp 22.3.

Presentation and course

In contrast to the delayed onset of the dominantly inherited ichthyosis vulgaris, scaling appears early, often soon after birth, and always by the first birth-day. The scales are larger and browner (Fig. 4.1), involve the neck, and to a lesser extent the popliteal and antecubital areas, as well as the skin generally. The palms and soles are normal. There is no association with atopy or keratosis pilaris. The condition persists throughout life. 

Complications

Corneal opacities may appear in adult life. Kallmann’s syndrome is caused by the deletion of a part of the X chromosome that includes the gene for X-linked recess-ive ichthyosis, which is therefore one of its features. Other features of this contiguous gene disorder are hypogonadism, anosmia and neurological defects.

Differential diagnosis

This is as for ichthyosis vulgaris. It is helpful to remember that only males are affected. Bear Kallmann’s syndrome in mind if there are other congenital abnormalities.

Investigations

None are usually needed. A few centres can measure steroid sulphatase in fibroblasts cultured from a skin biopsy.

Treatment

Oral aromatic retinoids are probably best avoided.

Topical measures are as for ichthyosis vulgaris.