👤 Abdüllatif Bakır

Maple syrup urine disease (MSUD) is a rare inborn error of metabolism caused by impaired catabolism of branched-chain amino acids (BCAAs). The genes BCKDHA, BCKDHB, DBT, and DLD encode the subunits of the branched-chain α-ketoacid dehydrogenase (BCKDH) complex, which is essential for BCAA metabolism. Catalytic subunits are BCKDHA, BCKDHB, DBT, and DLD, whereas the regulator subunits are PPM1K and BCKDK. PPM1K plays a critical role by dephosphorylating and activating this enzyme complex. Pathogenic variants in the PPM1K gene cause an extremely rare, mild form of MSUD. Here, we report an 8-year-old male patient with a mild form of MSUD putatively caused by a novel homozygous variant in PPM1K. The patient presented with mild dysmorphic features, delayed speech, relative microcephaly, and overweight, all considered familial phenotypic traits. Laboratory findings revealed mildly elevated plasma branched-chain amino acids, mild lactic acidemia, and a slight increase in urinary keto acids. Exome sequencing identified a novel homozygous missense variant, c.925A>G p.(Ile309Val), in the PPM1K gene. This case represents the third reported patient with a mild form of MSUD associated with the first reported missense variant in the PPM1K gene in the literature, further expanding the clinical and genetic spectrum of PPM1K-related disorders. Show less

Hypertrophic cardiomyopathy is a common genetic heart disease and up to 40%-60% of patients have mutations in cardiac sarcomere protein genes. This genetic diagnosis study aimed to detect pathogenic or likely pathogenic sarcomeric and non-sarcomeric gene mutations and to confirm a final molecular diagnosis in patients diagnosed with hypertrophic cardiomyopathy. A total of 392 patients with hypertrophic cardiomyopathy were included in this nationwide multicenter study conducted at 23 centers across Türkiye. All samples were analyzed with a 17-gene hypertrophic cardiomyopathy panel using next-generation sequencing technology. The gene panel includes ACTC1, DES, FLNC, GLA, LAMP2, MYBPC3, MYH7, MYL2, MYL3, PLN, PRKAG2, PTPN11, TNNC1, TNNI3, TNNT2, TPM1, and TTR genes. The next-generation sequencing panel identified positive genetic variants (variants of unknown significance, likely pathogenic or pathogenic) in 12 genes for 121 of 392 samples, including sarcomeric gene mutations in 30.4% (119/392) of samples tested, galactosidase alpha variants in 0.5% (2/392) of samples and TTR variant in 0.025% (1/392). The likely pathogenic or pathogenic variants identified in 69 (57.0%) of 121 positive samples yielded a confirmed molecular diagnosis. The diagnostic yield was 17.1% (15.8% for hypertrophic cardiomyopathy variants) for hypertrophic cardiomyopathy and hypertrophic cardiomyopathy phenocopies and 0.5% for Fabry disease. Our study showed that the distribution of genetic mutations, the prevalence of Fabry disease, and TTR amyloidosis in the Turkish population diagnosed with hypertrophic cardiomyopathy were similar to the other populations, but the percentage of sarcomeric gene mutations was slightly lower. Show less