Keratitis-ichthyosis-deafness syndrome, atypical connexin GJB2 genemutation, and peripheral T-cell lymphoma: more than a random association?

Keratitis-ichthyosis-deafness (KID) syndrome is a rare congenital disorder characterized by a variety of skin lesions— that is, palmoplantar keratoderma, thickening of the skin, and erythematous verrucous lesions—neurosensorial hypoacusia, and keratitis with a variable degree of visual impairment. Both sporadic and familial forms of the syndrome have been described, the latter usually showing a dominant pattern of inheritance. The molecular lesion responsible for the syndrome typically involves the connexin 26 (Cx26) gene (GJB2). Most patients display the heterozygous c.148G→A mutation causing the substitution of an aspartic acid for an asparagine at position 50 (p.Asp50Asn), while a few of them show the c.50C→T mutation, implying the substitution of a serine for a phenylalanine at position 17 (p.Ser17Phe). However, even a mutation in the connexin 30 (Cx30) gene (GJB6) has been found in a typical KID patient, thus suggesting a genetic heterogeneity of the syndrome. As connexins are a large family of small integral membrane proteins which influence tissue cornification by modulating the establishment of direct cell-cell communication through gap junction channels, it is likely that defects involving this class of proteins are at the basis of the wellknown increased incidence of squamous cell carcinoma in KID patients.