First report of the coexistence of dyschromatosis symmetrica hereditaria and psoriasis: one novel TCT to A mutation in the double‐RNA‐specific adenosine deaminase gene

Editor Dyschromatosis symmetrica hereditaria (DSH) (MIM 127400) is a rare pigmentary genodermatosis characterized by a mixture of hyperpigmented and hypopigmented macules of various sizes on the dorsal aspects of the extremities. Mutations in the doublestranded RNA specific adenosine deaminase (DSRAD) gene, composed of 15 exons spanning approximately 30 kb on chromosome 1q21.3, have been identified as the molecular basis of DSH. Psoriasis (MIM 177900) is relatively a common disease in the dermatological field. We herein present the first report of the coexistence of DSH and psoriasis in a 28-year-old man, who was harbouring a novel TCT to A mutation in the DSRAD gene. The DSH pedigree (Fig. 1a) consisted of twelve individuals, spanning three generations. The proband had developed an asymptomatic mixture of hyperpigmented and hypopigmented small macules on the dorsal aspects of the hands since 3 years old. The lesions were exacerbated by sun exposure. In addition, he had widespread symmetrical erythematous scaling plaques on body (Fig. 1b). A clinical diagnosis of psoriasis had been made at the age of 21 years, seven years previously, but he had no family history of psoriasis. Based on clinical and histological findings, coincident DSH and psoriasis were diagnosed. Following informed consent, EDTA blood was obtained and genomic DNA was isolated. All the coding regions of the DSRAD gene were amplified by Touchdown polymerase chain reaction (PCR). Purified PCR products were directly sequenced on an ABI 3730. We detected a heterozygous mutation at codon 878 in exon 8 in the DSRAD gene in the proband, comprised of a single nucleotide transversion (T to A at the base 2632) and two nucleotide deletion (2633-2634delCT) (Fig. 2), which were not described in the previous study. The same mutation was also found in his elder sister and nephew, but not in 100 unrelated controls and the healthy individuals of the family except his daughter, an asymptomatic carrier. The mutation consisting of a 1-base missense and 2-base deletion (TCT fi A) is predicted to generate a frameshift and a premature downstream stop codon in exon 9 located in the putative deaminase domain, resulting in truncated proteins (1–897 amino acids) likely without any functional activity. Psoriasis affects around 2% of the general population in the US and Europe and 0.123% in Chinese. Although the exact prevalence of DSH in China is not known, DSH has been reported mainly among Asian people with a prevalence of approximately 1.5 per 100 000 in the Japanese population. Associations between psoriasis and several comorbidities, including autoimmune disorders, metabolic syndrome, osteoporosis and depression and other dermatoses have been reported. However, the coexistence of DSH and other diseases is uncommon. Patients with DSH associated with idiopathic torsion dystonia, neurofibromatosis had already been reported. In 2006, Tojo reported a mutation of p.G1007R in the DSRAD gene in a