👤 Nisha Bhavani

Heterozygous familial hypercholesterolemia (FH), a monogenic cause for premature coronary artery disease (CAD) is often underdiagnosed. In individuals who meet the FH diagnostic criteria and lack pathogenic variants, polygenic factors are recognized as potential contributors. This study aimed to characterize the spectrum of genetic variants and determine the low-density lipoprotein polygenic risk score (LDL-PRS) among clinically diagnosed FH participants from South India. We recruited 116 unrelated participants with a pretreatment LDL- C concentration ≥ 190 mg/dl and a DLCN (Dutch Lipid Clinic Network) score ≥ 3. Targeted next-generation sequencing (NGS) of 23 lipid related genes and 12-SNP (Single nucleotide polymorphism) genotyping were performed. NGS identified 39 variants including 13 pathogenic and 26 variants of unknown significance (VUS) some of which were in non-classical genes: ABCG5, ABCG8, APOE, PPP1R17, SREBF2. Pathogenic variants were detected in 66.7% of those with definite FH,19.7% in probable FH and 2.7% in possible FH. Overall,66% were variant negative. Among variant negative (FH/V-) participants, 64% demonstrated high LDL-PRS, whereas 70% of variant positive participants also exhibited elevated scores; suggesting a contributory role of polygenic factors across both groups. Additionally, the observation that variant positive individuals with high LDL-PRS have an increased risk of coronary artery disease (CAD) adds important nuance to risk stratification within genetically confirmed FH patients. Confirmation of diagnosis by genetic testing is essential for the diagnosis of FH. Although LDL-PRS may offer little benefit in variant negative cases and improve CAD risk prediction in variant positive individuals, large scale studies are essential to validate its clinical utility and assess whether inclusion of additional LDL- raising SNPs could enhance the detection of polygenic FH in the Indian population. Show less

Dyggve-Melchior-Clausen dysplasia (DMC) and Smith-McCort dysplasia (SMC types 1 and 2) are rare spondyloepimetaphyseal dysplasias with identical radiological findings. The presence of intellectual disability in DMC and normal intellect in SMC differentiates the two. DMC and SMC1 are allelic and caused by homozygous or compound heterozygous variants in Detailed clinical phenotyping and skeletal radiography followed by molecular testing were performed in all affected individuals. Next-generation sequencing and Sanger sequencing were used to confirm 24 affected individuals from seven centres are described. 18 had DMC and 6 had SMC2. Parental consanguinity was present in 15 of 19 (79%). Height <3 SD and gait abnormalities were seen in 20 and 14 individuals, respectively. The characteristic radiological findings of lacy iliac crests and double-humped vertebral bodies were seen in 96% and 88% of the affected. Radiological findings became attenuated with age. 23 individuals harboured biallelic variants in either This large cohort from India contributes to the increasing knowledge of clinical and molecular findings in these rare 'Golgipathies'. Show less

Smith-McCort dysplasia (SMC OMIM 615222) and Dyggve-Melchior-Clausen dysplasia (DMC OMIM 223800) are allelic skeletal dysplasias caused by homozygous or compound heterozygous mutations in DYM (OMIM 607461). Both disorders share the same skeletal phenotypes characterized by spondylo-epi-metaphyseal dysplasia with distinctive lacy ilia. The difference rests on the presence or absence of intellectual disability, that is, intellectual disability in DMC and normal cognition in SMC. However, genetic heterogeneity was suspected in SMC. Recently, RAB33B (OMIM 605950) has been identified as the second gene for SMC. Nevertheless, only two affected families have been reported so far. Here we present three SMC patients with four novel pathogenic variants in RAB33B, including homozygosity for c.211C>T (p.R71*), homozygosity for c.365T>C (p.F122S), and compound heterozygosity for c.48delCGGGGCAG (p.G17Vfs*58) and c.490C>T (p.Q164*). We also summarize the clinical, radiological, and mutation profile of RAB33B after literature mining. This report ascertains the pathogenic relationship between RAB33B and SMC. © 2017 Wiley Periodicals, Inc. Show less