Clinico-genetic study of nail-patella syndrome

Nail-patella syndrome (NPS) is an autosomal dominant disease that typically involves the nails, knees, elbows and the presence of iliac horns. In addition, some patients develop glomerulopathy or adult-onset glaucoma. NPS is caused by loss-of-function mutations in the LMX1B gene. In this study, phenotype-genotype correlation was analyzed in 9 unrelated Korean children with NPS and their affected family members. The probands included 5 boy and 4 girls who were confirmed to have NPS, as well as 6 of their affected parents. All of the patients (100%) had dysplastic nails, while 13 patients (86.7%) had patellar anomalies, 8 (53.3%) had iliac horns, 6 (40.0%) had elbow contracture, and 4 (26.7%) had nephropathy including one patient who developed end-stage renal disease at age 4.2. The genetic study revealed 8 different LMX1B mutations (5 missense mutations, 1 frame-shifting deletion and 2 abnormal splicing mutations), 6 of which were novel. Genotype-phenotype correlation was not identified, but inter- and intrafamilial phenotypic variability was observed. Overall, these findings are similar to the results of previously conducted studies, and the mechanism underlying the phenotypic variations and predisposing factors of the development and progression of nephropathy in NPS patients are still unknown.