Genetic and allelic heterogeneity in 248 Indians with skeletal dysplasia

Abstract

Skeletal dysplasias are a clinically and genetically heterogeneous group of rare disorders. Studies from large cohorts are essential to provide insights into the disease epidemiology, phenotypic spectrum, and mutational profiles. Here we enumerate additional 248 Indians from 197 families with a skeletal dysplasia, following a similar study earlier. We achieved a clinical-molecular diagnosis in 145 families by targeted analysis in 37 and next generation sequencing (exomes and genomes) in 108 families that resulted in a diagnostic yield of 73.6% (145 of 197 families). We identified 149 causal variants, of which 85 were novel, across 73 genes. Eighty-one distinct monogenic forms of skeletal dysplasia were observed with a high proportion of autosomal recessive skeletal dysplasias (60%, 84 families). We observed consanguinity in 35% of the families. Lysosomal storage diseases with skeletal involvement, FGFR3-related skeletal dysplasia and disorders of bone mineralisation were most frequent in this cohort. We expand the phenotypic and genotypic spectrum of rarely reported conditions (RAB33B, TRIP11, NEPRO, RPL13, COL27A1, PTHR1, EXOC6B, PRKACA, FUZ and RSPRY1) and noted novel gene-disease relationships for PISD, BNIP1, TONSL, CCN2 and SCUBE3 related skeletal dysplasia. We successfully implemented genomic testing for skeletal dysplasia in clinical and research settings. Our study provides valuable information on the spectrum of skeletal dysplasia and disease-causing variants for Asian Indians.

Fig. 1. Flow chart outlining our study design for evaluation of skeletal dysplasia.

The numbers refer to the families that underwent the specific diagnostic test.