Two brothers are seen during a medical mission in Africa for their dry skin. The clinician recognizes the pattern of X-linked ichthyosis sparing the antecubital fossae of the arms amidst the heavy scales (Figure 171-1). With the help of a translator, the condition is explained to the mother and her boys. It turns out the mother’s father also had the same condition but never received a diagnosis or had any medical care. The suggested treatment is daily emollients and keratolytics.
Ichthyoses were recently reclassified by consensus with respect to nomenclature and whether they involved organs in addition to the skin (syndromic).1 This chapter addresses four relatively more common ichthyoses pediatricians may encounter: ichthyosis vulgaris, X-linked recessive ichthyosis, epidermolytic ichthyosis, and lamellar ichthyosis. Common features of the ichthyoses include thick, dry skin, various forms and degrees of scaling, cutaneous inflammation, hypohidrosis, and skin fragility. Management is typically symptomatic, attempting to reduce morbidity, and often involves coordinated care with a dermatologist.
Epidermolytic ichthyosis (EI)—Formerly known as epidermolytic hyperkeratosis (EHK) or bullous ichthyosiform erythroderma (BIE), nonbullous congenital ichthyosiform erythroderma (NBIE) or congenital ichthyosiform erythroderma (CIE).
Lamellar ichthyosis—Also known as nonbullous congenital ichthyosis, one of the autosomal recessive congenital ichthyoses (ARCI).
Ichthyosis vulgaris—A common ichthyosis (Figure 171-2), with approximately 1 in 250 individuals affected.2 Males and females are affected equally.
X-linked recessive ichthyosis—Occurs in approximately 1 in 2000 to 6000 males.3 Because of its frequent occurrence, steroid sulfatase deficiency accounts for most cases of X-linked ichthyosis, but a normal steroid sulfatase level in a male with ichthyosis does not rule out an X-linked pattern of inheritance.4
Epidermolytic ichthyosis (bullous ichthyosiform erythroderma)—Prevalence of approximately 1 in 200,000 to 300,000 persons.5
Lamellar ichthyosis (non-bullous ichthyosiform erythroderma)—The most common form of autosomal recessive congenital ichthyosis (Figure 171-3).6,7
FIGURE 171-3
Lamellar ichthyosis is more rare and severe than X-linked ichthyosis. A. Note the deep lines and severe dryness of the skin on the face of this girl with lamellar ichthyosis. B. Her arm is severely affected so that she cannot extend her elbow fully. (Used with permission from Richard P. Usatine, MD.)
Ichthyosis vulgaris—A relatively common condition caused by loss of function mutations in the filaggrin gene.2,8 It is inherited in an autosomal dominant manner and presents in childhood with a fine adherent scale in similar distribution to X-linked ichthyosis (Figure 171-2). Patients frequently have hyperlinear palms, keratosis pilaris, and atopic dermatitis, which are not commonly associated with X-linked ichthyosis.
X-linked ichthyosis—A deletion of the steroid sulfatase gene results in keratinocyte retention by inhibiting desmosome degradation.9 It is inherited in an X-linked recessive manner (Figure 171-4).
Epidermolytic ichthyosis—Inherited in an autosomal dominant manner and is due mutations leading to production of faulty keratin proteins that function poorly.10
Lamellar ichthyosis—A more severe and rare disorder resulting from mutations in the transglutaminase 1 gene.11 Manifests with plate-like scales involving most of the body, including the face and flexures (Figure 171-3). Patients are typically born as a collodion baby (a thin translucent membrane that surrounds the baby at birth).12
