Rare case of Cockayne syndrome with xeroderma pigmentosum.

Sir, Xeroderma pigmentosum (XP) and Cockayne syndrome (CS) are rare genodermatoses characterized by hypersensitivity to ultraviolet light. XP is a hereditary autosomal recessive condition, manifested clinically by abnormal photosensitivity of the skin and eyes, pigment anomalies, increased risk of cutaneous neoplasms and, frequently, by progressive neural degeneration (1 ± 3). CS is a rare autosomal recessive disorder of early aging. Its clinical picture and biochemical basis bears many similarities to XP, but some features are distinctly different. A full-blown clinical picture is characterized by growth retardation (so-called cachectic dwar®sm, with body weight being more affected than height), progressive neural degeneration, mental retardation, progressive pigmental retinopathy, hearing loss and skin photosensitivity. In contrast to XP, patients with isolated CS do not develop skin cancers (4). A few years ago it was thought that these 2 diseases were totally distinct entities caused by a speci®c mutation and distinctly defective scope of nucleotide excision repair. However, lately most researchers believe that mutations in nucleotide excision repair pathway genes can lead to XP, CS, trichotiodystrophy, or any combination of them, phenotypic expression depending on the site and type of mutation and the allelic heterogeneity of the genome (5 ± 7). We present data on a patient whose genome probably harboured a speci®c combination of mutations producing a rare double clinical syndrome consisting of XP and CS.