Abstract
Ring chromosome 15 [r(15)] syndrome is characterised by specific facial features, cafe au lait spots, failure to thrive, mental retardation and typically with a terminal deletion of the long arm of chromosome 15. We report a 2.5 year old girl showing normal growth and development, large hyperpigmented skin changes showing hypopigmentated areas inside, multiple cafe au lait spots and premature graying-like hypopigmentation of scalp hair. She had a karyotype of r(15) in peripheral lymphocytes and fibroblasts. By FISH analysis the breakpoint was located distal to locus D15S936 (15q26.3) and within 300 kb of the end of the chromosome, indicating no deletion of functional genes on 15q. Hyperpigmentation and cafe au lait spots are rare signs in ring chromosome syndromes, but with r(15) syndrome, cafe au lait spots have been described in about 30% of patients and have been considered to result from the deletion of gene(s) on distal 15q. Based on the frequent observation of patchy hyperpigmentation with the r(15) syndrome, absent hyperpigmentation in cases of distal 15q deletion without a ring chromosome, and the telomeric breakpoint location in our patient indicating no significant deletion, we propose that the cutaneous hyperpigmentation and cafe au lait spots in our proband represent effects of the r(15) chromosome but are not caused by the deletion of specific gene(s) on distal 15q. Patchy skin hypopigmentation is a well known nonspecific sign in cytogenetic mosaicism which is commonly seen in ring syndrome.
