CONGENITAL ICHTHYOSIFORM

 

 ERYTHRODERMA

 

As with lamellar ichthyosis, CIE is apparent at birth, and the newborn usually presents with a taut, shiny, collodion membrane. After shedding of the membrane, the skin of infants with CIE remains red, usually with a fine, white, generalized scale . On the lower legs, the scale may be larger and darker. In contrast to lamellar ichthyosis, the classic presentation of CIE has little to no ectropion, eclabium, or alopecia. As in lamellar ichthyosis, there is a wide variation in the ability to sweat, and patients with CIE may have minimal sweating with severe heat intolerance. Mucous membranes are usually spared. Palm/sole involvement is variable. Nails may have ridging, but they are often spared. As with all the ichthyoses, dermatophyte infection of the skin and nails is common.

Histopathologic examination shows hyperkeratosis, acanthosis, and often parakeratosis . Studies of epidermal proliferation have shown markedly increased epidermal cell turnover, in contrast to lamellar ichthyosis.

A small subset of patients with CIE have been found to have mutations in TGM1, and two siblings with a collodion presentation, CIE, and palmoplantar keratoderma had an autosomal dominant mutation in the cornified envelope protein, loricrin.⁵⁴ Further genetic heterogeneity within ARCI has been demonstrated, with exclusion of TGM1 as the disease-causing gene in families with phenotypes within the spectrum of classic lamellar ichthyosis and CIE and identification of mutations in other genes. To date, mutations have been identified in five additional genes in nonsyndromic ARCI, and in two additional genes in two forms of syndromic ARCI. In addition, two other genetic loci (12p11.2-q13 and 19p13.1-13.2) have been found to be associated with ARCI; the responsible genes have not been identified . A newly described, lipoxygenase pathway has been hypothesized as a common pathway linking many of the ARCIs. This hypothesis remains to be tested, and how the most common mutation in ARCI, that of TGM1, might relate to lipid abnormalities is unclear.