The genotypic and phenotypic landscape of PDHA1-related pyruvate dehydrogenase complex deficiency

This retrospective study on X-linked PDHA1-related pyruvate dehydrogenase complex (PDHc) deficiency combined a systematic literature review with a multicentre survey exploring genotypes, phenotypes and survival. Data from 891 individuals (45% unpublished) were included. Of note, 53% of cases were females. Median age at last assessment was 6 years (range 0-80 years, n = 622). We detected 331 different (118 unpublished) PDHA1 variants, of which 75% (305/405) had occurred de novo. Variants in this study were uploaded to ClinVar (SCV006297015-SCV006297345). The 10 most frequent variants accounted for 36% of the diagnoses. Sixty-nine per cent of the variants were private; missense (50%) and frameshift (20%) variants were most common. Frameshift/nonsense (FS/N) variants in males (44/401, 11%) were confined to regions escaping nonsense-mediated decay (NMD) and were significantly less frequent than in females (151/461, 33%). Neonatal or infantile (405/529, 77%) presentations were most frequent, with pre/perinatal abnormalities reported in 47% (159/342). FS/N variants in the NMD-predicted region 3.9 [95% confidence interval (CI) 1.54-11.04] times increased the odds of fetal findings. Females presented significantly earlier [2 months, interquartile range (IQR) 7.0, n = 224] than males (8 months, IQR 16.6, n = 233), with increased risk of neonatal presentation [odds ratio (OR) 3.01 (95% CI 1.279-7.616)] when harbouring FS/N variants in the NMD-predicted region. The overall (n = 242) mean survival time was 10.9 (95% CI 9.9-11.9) years. On average, females survived 4.5 (95% CI 2.62-6.40) years longer than males despite presenting more severe phenotypes. Poor survival was associated with male sex [hazard ratio (HR) 3.3 (95% CI 1.95-5.62)], neonatal presentation [HR 5.5 (95% CI 2.17-14.09)], FS/N variants in the NMD-predicted region [HR 4.0 (95% CI 1.78, 9.16)] and splice variants [HR 2.3 (95% CI 1.15, 4.59)]. More severe clinical phenotypes were predicted by neonatal or infantile presentations and by female sex. Developmental delay (DD), intellectual disability (ID), muscle hypotonia, abnormal movements, seizures, feeding difficulties and microcephaly were the most frequent phenotypes, all occurring in more than half. Corpus callosum or basal ganglia alterations and cerebral atrophy were common. Four per cent (36/891) were reported to have mild phenotypes with no DD nor ID (25/36 males). This is the largest dataset on a nuclear-encoded defect of mitochondrial energy metabolism. The genotypic and phenotypic details further defines the disease landscape and can be used for variant interpretation. The correlations between genotypes, sex, phenotypes and survival, adds substantial improvement to counselling.