Ichthyosis hystrix

Synonyms: ichthyosis hystrix gravior, epidermolytic hyperkeratosis (EHK) or bullous congenital ichthyosiform erythroderma, Lambert type ichthyosis

What is ichthyosis hystrix?¹

Ichthyosis hystrix is used to describe several rare ichthyosis skin disorders and is characterised by massive hyperkeratosis with an appearance like spiny scales.

The term has also been used to describe localised and linear warty epidermal nevi sometimes associated with mental retardation, seizures or skeletal anomalies. Alopecia, and hair and nail abnormalities as well as inner ear deafness are also seen.

The condition was first described in the Lambert family in England in the early 18th century..

The designation of epidermolytic hyperkeratosis is used for the condition that is also called bullous congenital ichthyosiform erythroderma² when generalised and ichthyosis hystrix when localised. They are presumably separate entities. Most types of ichthyosis are hereditary rather than acquired.

Ichthyosis hystrix epidemiology

This is a rare condition of autosomal dominant inheritance, although sporadic cases do occur. Ichthyosis hystrix is not only a rare disorder but may also be clinically heterogeneous, even within the same family.³

Ichthyosis hystrix symptoms (presentation)

It is apparent at birth or in the neonatal period as erythema with blistering affecting either a localised area of skin, or it can be more generalised. Blisters then heal with apparently normal skin but can recur. However, skin gradually becomes hyperkeratotic and scaly, particularly in flexures. Scales are hard and verruciform with parallel ridges running over the flexures, neck and hips. There is often a characteristic smell of rancid butter.

The whole body is affected, with the exception of the face, genitals, palms and soles.

Differential diagnosis^{4 5}

There are about 25 different forms of ichthyosis and obviously the generalist will not be expected to recognise each. Differing features include age at onset, the appearance of the skin, areas that may be affected or spared including flexures, palms, soles and face. The family history may also be indicative. Skin biopsy may be helpful. There may be features that are not dermatological that point to a specific syndrome.

The most common form of ichthyosis is ichthyosis vulgaris.

Investigations⁶

• Biopsy and electron microscopy may be useful in the early diagnosis of genetic disorders. Skin biopsy shows characteristic changes.

• Analysis of cellular DNA.

Ichthyosis hystrix treatment and management¹

There is no specific treatment for ichthyosis hystrix. Treatment consists of symptomatic therapy for complications and cosmetic purposes. Topical retinoids, usually tretinoin, may be beneficial. Etretinate may be effective.

Hydration of the skin and application of an ointment to prevent evaporation:

• Lactic, glycolic and pyruvic acids are effective for hydrating the skin. Lactic acid is available as a 5% proprietary preparation. Twice-daily applications have been shown to be superior to petroleum-based creams for control of ichthyosis.

• Removal of scales can be aided by keratolytics such as salicylic acid.

• Proprietary products often contain urea or propylene glycol. Moisturisers containing urea in lower strengths such as 10 or 20%, produce a more pliable stratum corneum by their hydratant action.

• Propylene glycol draws water through the stratum corneum by establishing a water gradient. Thick skin is then shed following hydration.

• Topical retinoids, usually tretinoin, may be beneficial. A good result with etretinate is reported.⁷

• Ichthyosis does not respond to steroids, but a mild topical steroid may be useful for pruritus.

Complications

This is a visible and unsightly condition that affects children and adolescents too. Hence they are likely to be cruelly teased and will lack confidence in amorous encounters.

Prevention

There does not appear to be any prenatal test that can be employed. As it is a dominant condition, presumably one parent is affected. The literature seems to make no reference to limited penetrance. There will be a 1 in 2 chance of any children being affected.