MedGenome Labs Ltd. – Publications | MedGenome - Part 2


At MedGenome, we are deeply focused on continuous innovation, and publishing our findings for the larger benefit of the genetic testing community. Read through our publications for details of our latest work.

Date: July 11, 2022

Objective To evaluate metabolic and genetic abnormalities in children with nephrolithiasis attending a referral center in North India. Methods The patients aged 1–18 y old with nephrolithiasis underwent biochemical evaluation and whole-exome sequencing. The authors evaluated for monogenic variants in 56 genes and compared allele frequency of 39 reported polymorphisms between patients and 1739 controls from the GenomeAsia 100 K database. Results Fifty-four patients, aged 9.1 ± 3.7 y were included. Stones were bilateral in 42.6%, familial in 33.3%, and recurrent in 25.9%. The most common metabolic abnormalities were hypercalciuria (35.2%), hyperoxaluria (24.1%), or both (11.1%), while xanthinuria (n = 3), cystinuria (n = 1), and hyperuricosuria (n = 1) were rare. Exome sequencing identified an etiology in 6 (11.1%) patients with pathogenic/likely pathogenic causative variants. Three variants in MOCOS and one in ATP7B were pathogenic; likely pathogenic variants included MOCOS (n = 2), AGXT, and SLC7A9 (n = 1, each). Causality was not attributed to two SLC34A1 likely pathogenic variants, due to lack of matching phenotype and dominant family history. Compared to controls, allele frequency of the polymorphism TRPV5 rs4252402 was significantly higher in familial stone disease (allele frequency 0.47 versus 0.53; OR 3.2, p = 0.0001).

Date: July 10, 2022

Parkinson’s disease (PD) is a genetically heterogeneous neurodegenerative disease with poorly defined environmental influences. Genomic studies of PD patients have identified disease-relevant monogenic genes, rare variants of significance, and polygenic risk-associated variants. In this study, whole genome sequencing data from 90 young onset Parkinson’s disease (YOPD) individuals are analyzed for both monogenic and polygenic risk. The genetic variant analysis identifies pathogenic/likely pathogenic variants in eight of the 90 individuals (8.8%). It includes large homozygous coding exon deletions in PRKN and SNV/InDels in VPS13C, PLA2G6, PINK1, SYNJ1, and GCH1. Eleven rare heterozygous GBA coding variants are also identified in 13 (14.4%) individuals. In 34 (56.6%) individuals, one or more variants of uncertain significance (VUS) in PD/PD-relevant genes are observed. Though YOPD patients with a prioritized pathogenic variant show a low polygenic risk score (PRS), patients with prioritized VUS or no significant rare variants show an increased PRS odds ratio for PD. This study suggests that both significant rare variants and polygenic risk from common variants together may contribute to the genesis of PD. Further validation using a larger cohort of patients will confirm the interplay between monogenic and polygenic variants and their use in routine genetic PD diagnosis and risk assessment.

Date: April 13, 2022

Abstract Background 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 DYM. SMC2 is caused by variations in RAB33B. Both DYM and RAB33B are important in intravesicular transport and function in the Golgi apparatus. Methods 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 DYM and RAB33B variants. Sanger sequencing of familial variants was done in all parents. Results 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 DYM or RAB33B. Fourteen different variants were identified, out of which 10 were novel. The most frequently occurring variants in this group were c.719 C>A (3), c.1488_1489del (2), c.1484dup (2) and c.1563+2T>C (2) in DYM and c.400C>T (2) and c.186del (2) in RAB33B. The majority of these have not been reported previously.

Date: April 13, 2022

Abstract The clinico-genetic architecture of sarcoglycanopathies in Indian patients is reported only as short series. In the present study, we aimed to investigate the clinical picture, genetic basis, and disease progression of patients genetically confirmed to have sarcoglycanopathy. Next-generation sequencing was performed in 68 probands with suspected sarcoglycanopathy. A total of 35 different variants were detected in the sarcoglycan genes in 68 probands (M = 37; age range, 5–50 years). Consanguinity was present in 44 families. Thirty-two variants are predicted to be pathogenic/likely pathogenic, among which 25 (78.13%) are reported, and 7 (21.87%) are novel. The clinical diagnosis was confirmed in a total of 64 (94.12%) probands with biallelic variations [SGCA(n=18); SGCB(n=34); SGCG(n=7); SGCD(n=5)]. The most common mutation was c.544A > C (p.Thr182Pro) in SGCB, and detected in 20 patients (29.42%). The majority of pathogenic mutations are homozygous (n = 30; 93.75%). Variants in 4 cases are of uncertain significance. Thirty-three patients lost ambulation at a mean age of 15.12 ± 9.47 years, after 7.76 ± 5.95 years into the illness. Only 2 patients had cardiac symptoms, and one had respiratory muscle involvement. The results from this study suggest that mutations in SGCB are most common, followed by SGCA, SGCG, and SGCD. The novel variations identified in this study expand the mutational spectrum of sarcoglycanopathies. To the best of our knowledge, this is the first study from India to describe a large cohort of genetically confirmed patients with sarcoglycanopathy and report its disease progression.

Date: January 13, 2022

Autosomal aneuploidies occurring in chromosomes other than 13, 18, and 21 and sex chromosomal aneuploidies are referred to as ‘Rare autosomal aneuploidies’ (RAAs).
A prenatal incidence of 0.41% is noted for RAAs on chorionic villus sampling (CVS) procedures. Aneuploidies in autosomes other than 13, 18, and 21 and sex chromosomal aneuploidies may result in increased fetal-placental diseases
such as non-viable pregnancy, early miscarriage, intrauterine fetal growth restriction, uniparental disomy, multiple congenital anomalies, fetal demise, or normal live birth [1]. The screen-positive rate of RAAs on NIPT is 0.04% to 0.83%.
However, the PPV of RAAs on NIPT is found to be 6–29%.
The increased false positives for RAAs on NIPT are most commonly due to confined placental mosaicism (CPM) [2] but may also arise due to vanishing twin or maternal malignancies.
Clinically relevant abnormalities can be detected in 30–75% of the high-risk cases of RAAs in NIPT [1].

Date: January 13, 2022

References 1. Hsieh L, Nugent D (2008) Factor XIII deficiency. Haemophilia 14:1190–1200 2. Loewy AG, McDonagh J, Mikkola H, Teller DC, Yee VC (2001) Structure and function of factor XIII. In: Colmam RW, Hirsh J, Marder VJ, Clowes AW, George JN (eds) Hemostatis and thrombosis: basic principles and practice. Lippincott Williams and Wilkins, Philadelphia, pp 233–247

Date: February 9, 2023

Ocular dyskinesia (OD) is an uncommon form of the levodopa induced dyskinesia (LIOD) characterized by short-lasting horizontal or upward conjugate gaze deviation. More sustained deviations resembling oculogyric crises (OGC) are distinctly uncommon.1-4 A 62-yr-old man with a 10-yr history of Parkinson’s disease (PD) presented florid ocular dyskinesia mimicking OGC. Levodopa introduction caused increased blinking, up rolling of the eyeballs and dose-dependent restlessness lasting 48 hr with a single dose of 300 mg. Amantadine, safinamide, clonazepam, and dopamine agonists were without benefit, and he stayed off medication for 3 yr. The symptoms recurred after restarting levodopa at age 61. There was no relevant tic, dopamine blocker, encephalitis, or family history. His OFF-UPDRS-III score was 78 (Video 1). Within 10–15 min of levodopa 100 mg increased eyeblink, blepharospasm, right-sided horizontal/upward conjugate eye movements, buccolingual and peribuccal dyskinesia were noted (Video 2). Apomorphine (4 mg) resulted in similar ocular features. MRI brain was normal. Whole-exome sequencing showed variants of unknown significance in GBA p.Arg170His (also in his asymptomatic older sister) and LRRK2 p.Arg1943Trp genes.

Date: January 6, 2022

Background Inherited tubulopathies are a heterogeneous group of genetic disorders making whole-exome sequencing (WES) the preferred diagnostic methodology. Methods This was a multicenter descriptive study wherein children (< 18 years) with clinically suspected tubular disorders were recruited for molecular testing through WES. Multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing were done when required. Variants were classified as per American College of Medical Genetics 2015 guidelines and pathogenic (P)/likely pathogenic (LP) variants were considered causative. Results There were 77 index cases (male =73%). Median age at diagnosis was 48 months (IQR 18.5 to 108 months). At recruitment, the number of children in each clinical group was as follows: distal renal tubular acidosis (dRTA) = 25; Bartter syndrome = 18; isolated hypophosphatemic rickets (HP) = 6; proximal tubular dysfunction (pTD) = 12; nephrogenic diabetes insipidus (NDI) = 6; kidney stone/nephrocalcinosis (NC) = 6; others = 4. We detected 55 (24 novel) P/LP variants, providing genetic diagnoses in 54 children (70%). The diagnostic yield of WES was highest for NDI (100%), followed by HP (83%; all X-linked HP), Bartter syndrome (78%), pTD (75%), dRTA (64%), and NC (33%). Molecular testing had a definite impact on clinical management in 24 (31%) children. This included revising clinical diagnosis among 14 children (26% of those with a confirmed genetic diagnosis and 18% of the overall cohort), detection of previously unrecognized co-morbidities among 8 children (sensorineural deafness n = 5, hemolytic anemia n = 2, and dental changes n = 1) and facilitating specific medical treatment for 7 children (primary hyperoxaluria n = 1, cystinosis n = 4, tyrosinemia n = 2).

Date: October 2, 2021

ABSTRACT Background. The burden of hereditary breast cancer in India is not well defined. Moreover, genetic testing criteria (National Comprehensive Cancer Network [NCCN] and Mainstreaming Cancer Genetics [MCG] Plus) have never been validated in the Indian population. Methods. All new female breast cancer patients from 1st March 2019 to 28th February 2020 were screened. Those providing informed consent and without previous genetic testing were recruited. Multigene panel testing (107 genes) by next-generation sequencing was performed for all patients. The frequency of pathogenic/likely pathogenic (P/ LP) mutations between patients qualifying and not qualifying the testing criteria was compared and their sensitivity was computed. Results. Overall, 275 breast cancer patients were screened and 236 patients were included (median age 45 years); 30 patients did not consent and 9 patients previously underwent genetic testing. Thirty-four (14%) women had a positive family history and 35% had triple-negative breast cancer. P/LP mutations were found in 44/236 (18.64%).

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