Open AccessPrenatal diagnosis of combined methylmalonic acidemia and homocystinuria cobalamin C type using clinical exome sequencing and targeted gene analysis
Author(s) -
Hwang Narae,
Jang JaHyun,
Cho EunHae,
Choi Rihwa,
Choi SukJoo,
Park HyungDoo
Publication year - 2021
Publication title -
molecular genetics and genomic medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 29
ISSN - 2324-9269
DOI - 10.1002/mgg3.1838
Subject(s) - methylmalonic acidemia , homocystinuria , exome sequencing , newborn screening , medicine , genetics , cobalamin , sanger sequencing , exome , methylmalonic aciduria , methylmalonic acid , pediatrics , biology , homocysteine , gene , dna sequencing , mutation , amino acid , vitamin b12 , methionine
Background Combined methylmalonic acidemia and homocystinuria is a rare inherited disorder of intracellular cobalamin metabolism caused by biallelic variants in one of the following genes: MMACHC (cblC), MMADHC (cblD), LMBRD1 (cblF), ABCD4 (cblJ), THAP11 (cblX‐like), and ZNF143 (cblX‐like), or a hemizygous variant in HCFC1 (cblX). Prenatal diagnosis of combined methylmalonic acidemia with homocystinuria is crucial for high‐risk couples since the disorder can be life‐threatening for offspring. We would like to describe two infant deaths both of which are likely attributable to cblC despite not having a genetic confirmation, and subsequent pregnancy and prenatal genetic testing. Methods Parental clinical exome sequencing and targeted Sanger sequencing of MMACHC gene in amniotic fluid was performed to check the carrier status of the fetus. Results Parental clinical exome sequencing revealed a heterozygous pathogenic variant [NM_015506.2:c.217C>T (p.Arg73*)] in the MMACHC gene of the mother and [NM_015506.2:c.609G>A (p.Trp203*)] in the MMACHC gene of the father. Targeted Sanger sequencing of MMACHC gene in amniotic fluid revealed that the fetus carried only one nonsense variant [NM_015506.2:c.609G>A (p.Trp203*)], which was inherited from the father. The mother delivered a healthy baby and the neonate did not show any symptoms or signs of combined methylmalonic acidemia and homocystinuria after birth. Conclusion We present a case of prenatal diagnosis with parental exome sequencing, which successfully diagnosed the carrier status of the fetus and parents in a combined methylmalonic acidemia and homocystinuria family.