Autosomal Recessive Congenital Ichthyosis

Abstract

Clinical characteristics Autosomal recessive congenital ichthyosis (ARCI) encompasses several forms of nonsyndromic ichthyosis. Although most neonates with ARCI are collodion babies, the clinical presentation and severity of ARCI may vary significantly, ranging from harlequin ichthyosis, the most severe and often fatal form, to lamellar ichthyosis (LI) and (nonbullous) congenital ichthyosiform erythroderma (CIE). These phenotypes are now recognized to fall on a continuum; however, the phenotypic descriptions are clinically useful for clarification of prognosis and management. Infants with harlequin ichthyosis are usually born prematurely and are encased in thick, hard, armor-like plates of cornified skin that severely restrict movement. Life-threatening complications in the immediate postnatal period include respiratory distress, feeding problems, and systemic infection. Collodion babies are born with a taut, shiny, translucent or opaque membrane that encases the entire body and lasts for days to weeks. LI and CIE are seemingly distinct phenotypes: classic, severe LI with dark brown, plate-like scale with no erythroderma and CIE with finer whiter scale and underlying generalized redness of the skin. Affected individuals with severe involvement can have ectropion, eclabium, scarring alopecia involving the scalp and eyebrows, and palmar and plantar keratoderma. Besides these major forms of nonsyndromic ichthyosis, a few rare subtypes have been recognized, such as bathing suit ichthyosis, self-improving collodion ichthyosis, or ichthyosis-prematurity syndrome. Diagnosis/testing The diagnosis of nonsyndromic ARCI is established by skin findings at birth and in infancy. Skin biopsy is not necessary to establish the diagnosis of ARCI. The twelve genes known to be associated with ARCI are ABCA12, ALOX12B, ALOXE3, CASP14, CERS3, CYP4F22, LIPN, NIPAL4, PNPLA1, SDR9C7, SLC27A4, and TGM1; at least 15% of affected families do not have pathogenic variants in any of the known genes. A multigene panel that includes these genes is the diagnostic test of choice. If such testing is not available, single-gene testing can be considered starting with ABCA12 in individuals with harlequin ichthyosis, TGM1 in individuals with ARCI without harlequin presentation at birth and SLC27A4 in those presenting with ichthyosis-prematurity syndrome. Management Treatment of manifestations: For neonates, a moist environment in an isolette, hygienic handling to prevent infection, and treatment of infections; petrolatum-based creams/ointments to keep the skin soft, supple, and hydrated; for older children, humidification with long baths, lubrication, and keratolytic agents such as alpha-hydroxy acid or urea preparations to promote peeling and thinning of the stratum corneum; for those with ectropion, lubrication of the cornea; for those with severe skin involvement, cautious use of oral retinoids. Prevention of secondary complications: Prevention of infection, dehydration and overheating, corneal drying; high caloric diet; when necessary, release of collodion membrane on digits to maintain circulation and on the thorax for adequate respiration. Surveillance: Regular physical examination for evidence of infection, management of skin involvement, as well as for the increased (but still low) risk for skin malignancy (squamous cell carcinoma, basal cell carcinoma, atypical melanocytic nevi, or malignant melanoma). Agents/circumstances to avoid: Skin irritants; overheating. Genetic counseling ARCI is inherited in an autosomal recessive manner. Each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if both ARCI-related pathogenic variants have been identified in a family.