Patients with DSH have a characteristic appearance including a mixture of hyperpigmented and hypopigmented macules of various sizes on the dorsal aspects of the hands and feet. Few patients have similar lesions on the knees and elbows. Many patients have frecklelike macules on the face and arms.1-6 One patient has been described with scattered depigmented spots on the face and chest.1 Our patient had a characteristic appearance as well as some special manifestations including skin lesions on the curved side of the wrist, ears, neck, and upper back.
The human ADAR1 gene spans 30 kilobase and contains 15 exons. It encodes RNA-specific adenosine deaminase composed of 1226 amino acid residues. This enzyme is important for various functions such as site-specific RNA editing and nuclear translation. This enzyme has 2 Z-alpha domains, 3 double-stranded RNA–binding domains, and the putative deaminase domain corresponding to exon 2, exons 2 to 7, and exons 9 to 14 of ADAR1, respectively.6
Mutation analysis of the ADAR1 gene in this case showed heterozygous insertion mutation c.2253insG in exon 6 of the ADAR1 gene, which changed the reading frame, and 475 amino acid residues in C-terminus are replaced by 90 amino acid residues (TSSRAQVRLPSKSWGSLVPSRLRTQQEA RQAGSSRCGSPCLDWGEREGRTHGFHRG NPSDRGQSQKNYAPPLKVPRSTAKT DTPSHWQHLP). This mutation was not detected in the proband’s healthy parents and the 100 control individuals, which indicated that it was a de novo mutation and the pathogenic mutation of DSH rather than a common polymorphism.
In conclusion, we report a novel mutation of the ADAR1 gene with a heavy clinical phenotype in DSH. This study expands the spectrum of clinical manifestations and demonstrates the ADAR1 mutation in DSH.
Acknowledgments
We are most grateful to the patient and her family for taking part in our study.