Ichthyosis vulgaris This is the mildest and most common form of ichthyosis, with an incidence in school-aged children as high as 1:250. It is inherited as an autosomal dominant trait and is present in a significant percentage of individuals with atopic dermatitis. It is not present at birth.

The clinical appearance of this ichthyosis varies, depending on location. Figures 15-1 and 15-2 illustrate the fine, bran-like scaling on the upper chest and back. Children with ichthyosis vulgaris are likely to have increased skin markings on the palms and soles and a high incidence of keratosis pilaris (see Figs. 15-61,15-62,15-63,15-64).

Ichthyosis vulgaris On the anterior lower leg, there are often larger, plate-like scales that resemble the skin of a fish (Figs. 15-3 and 15-4). Facial involvement is usually minimal, and flexural areas are typically spared.

Ichthyosis vulgaris tends to worsen in winter when there is less sweating and lower humidity. Treatment of ichthyosis vulgaris entails the use of emollients and creams and ointments containing urea, lactic acid, and other alpha-hydroxy acids. Excessive bathing and the use of alkaline soaps should be avoided. The exacerbation that frequently occurs in winter months can be lessened if a humidifier is used in the child’s room.

Harlequin–type ichthyosis The newborn infant is covered with thick plates of scale that are often described as resembling a coat of armor. After birth, deep erythematous fissures form between areas of scale. There is also severe facial disfigurement due to eclabium, ectropion, and edema of the conjunctiva. The texture of the skin results in restriction of the respiratory movements of the chest and interferes with normal feeding. This form of ichthyosis is due to a mutation on the ABCA12 gene.

Collodion baby This is a descriptive term for the child who is born encased in a taut, parchment-like membrane, accompanied by ectropion and eclabium. The outcome of this process is unpredictable. When the membrane is completely shed, the infant may go on to develop one of several ichthyosis skin types. Lamellar ichthyosis and congenital ichthyosiform erythroderma (pictured in Fig. 15-6) are the most common. A small percentage of infants go on to have completely normal skin, a phenomenon called “self-healing collodion baby.”

Collodion baby Collodion babies are at risk for complications. These include infection, dehydration, body temperature instability, and pneumonia. Collodion babies should be placed in a high humidity environment, and monitored closely. Gradually, the membrane will come off on its own. The child pictured in Fig. 15-7 also developed congenital ichthyosiform erythroderma.

Figure 15-8 is an example of more severe form of collodion baby, with marked ectropion. After spontaneous shedding of the collodion membrane, this child went on to develop lamellar ichthyosis (Figs. 15-9,15-10,15-11,15-12,15-13,15-14,15-15,15-16).

Lamellar ichthyosis Collodion babies, irrespective of the cause, are very often born prematurely. In addition, they are at risk for cutaneous infection, sepsis, pneumonia, and require careful supportive therapy. This infant was formerly a collodion baby and has gradually sloughed his membrane. When the baby was several months of age, he began to develop generalized hyperkeratosis and scaling. This infant has the chronic and severe autosomal recessive disease of lamellar ichthyosis.

The child in Fig. 15-10 has severe facial involvement. Note the ectropion and tightness of the facial skin as a result of hyperkeratosis. Plate-like scales of the forehead are a particularly common feature.

Lamellar ichthyosis Figure 15-11 shows in detail the kind of ichthyosis that gradually becomes established after the disappearance of the collodion membrane. Note the mosaic pattern of the scales and tendency of the edges of the scale to curl away from the surface. The scales are sometimes compared with armored plates. Blister formation does not occur in this condition.

In severe cases, the entire skin surface, including the face, is affected by the hyperkeratotic, scaly, dyschromic dyskeratinization. Involvement tends to be most severe in flexural areas, as in the axilla pictured in Fig. 15-12. Topical therapy with the α-hydroxy acids, such as lactic acid, or with topical N-acetylcysteine is somewhat helpful in reducing the amount of scale and improving the appearance.

Lamellar icthyosis In this severe example, there is thick and dark scale involving the entire face, as well as severe ectropion. For many children, eye involvement like this is the most disfiguring aspect of the disease. In addition, scaliness of the scalp may be accompanied by partial hair loss.

This patient has developed thick scale involving the entire skin surface. One form of lamellar ichthyosis is associated with a deficiency of the enzyme keratinocyte transglutaminase.

Lamellar ichthyosis Figures 15-15 and 15-16 illustrate involvement of the palms and soles with thick hyperkeratosis and deep grooves.

In addition to thickening and fissuring of the palms and soles, the nails may be ridged or thickened, and there may be thick subungual hyperkeratosis.

Recessive X-linked ichthyosis This disorder is characterized by ichthyosis that begins at or shortly after birth and persists through adult life. The “dirty” brown and tightly adherent scales are illustrated in Figs. 15-17, 15-18, 15-19. The scaling tends to favor the trunk and the extensor surfaces of the extremities. There is relative sparing of the face and flexural areas.

The palms and soles are also spared, and the hair and teeth are normal. Most patients note marked improvement during the summer months, probably related to improved skin hydration. Asymptomatic corneal opacities on the posterior membrane serve as an adult marker for this disease.

Recessive X-linked ichthyosis In addition, there is a significant incidence of cryptorchidism in individuals with this syndrome. The locus for this rare genodermatosis is now known to affect the STS (steroid sulfatase) gene on the distal short arm of the X chromosome, and the disease is inherited in X-linked recessive fashion. The underlying metabolic disorder is a deficiency in the enzyme steroid sulfatase.

Figure 15-20 gives a closer view of the tightly adherent scales that are seen in this hereditary disorder.

Epidermolytic ichthyosis (formerly epidermolytic hyperkeratosis) The appearance of epidermolytic ichthyosis in a newborn is illustrated in Fig. 15-21. Typically, there are large areas of denuded skin, and sometimes there are intact blisters. The differentiation from epidermolysis bullosa can usually be made by positive family history, the presence of subtle areas of hyperkeratosis, and, most important, the characteristic skin biopsy. Treatment in the newborn period should focus on gentle handling to avoid new blister formation, the maintenance of fluid and electrolyte balance, and the prevention of bacterial superinfection.

Over time, the generalized blistering resolves, and widespread areas of thick hyperkeratosis and scale develop. In Fig. 15-22, there is a mixed picture; focal erosions are present on the arms and abdomen, and there are areas of thick, discolored, furrowed hyperkeratosis. Note the predilection, which is not seen in ichthyosis vulgaris, for the antecubital fossae and intertriginous spaces.