The phenotype of a germline mutation in PIGA: the gene somatically mutated in paroxysmal nocturnal hemoglobinuria.

Phosphatidylinositol glycan class A (PIGA) is involved in the first step of glycosylphosphatidylinositol (GPI) biosynthesis. Many proteins, including CD55 and CD59, are anchored to the cell by GPI. Loss of CD55 and CD59 on erythrocytes causes complement-mediated lysis in paroxysmal nocturnal hemoglobinuria (PNH), a disease that manifests after clonal expansion of hematopoietic cells with somatic PIGA mutations. Although somatic PIGA mutations have been identified in many PNH patients, it has been proposed that germline mutations are lethal. We report a family with an X-linked lethal disorder involving cleft palate, neonatal seizures, contractures, central nervous system (CNS) structural malformations, and other anomalies. An X chromosome exome next-generation sequencing screen identified a single nonsense PIGA mutation, c.1234C>T, which predicts p.Arg412(∗). This variant segregated with disease and carrier status in the family, is similar to mutations known to cause PNH as a result of PIGA dysfunction, and was absent in 409 controls. PIGA-null mutations are thought to be embryonic lethal, suggesting that p.Arg412(∗) PIGA has residual function. Transfection of a mutant p.Arg412(∗) PIGA construct into PIGA-null cells showed partial restoration of GPI-anchored proteins. The genetic data show that the c.1234C>T (p.Arg412(∗)) mutation is present in an affected child, is linked to the affected chromosome in this family, is rare in the population, and results in reduced, but not absent, biosynthesis of GPI anchors. We conclude that c.1234C>T in PIGA results in the lethal X-linked phenotype recognized in the reported family.

MRI features of 4 female patients with pyruvate dehydrogenase E1 alpha deficiency.

Pyruvate dehydrogenase complex is a key intramitochondrial multienzyme complex required for the conversion of pyruvate to acetyl-CoA. Most patients with pyruvate dehydrogenase deficiency have a defect in the E1 alpha subunit, associated with mutations in the PDHA1 gene. In this report, we submit detailed magnetic resonance images in 4 affected female patients with PDHA1 mutations who had with severe cortical atrophy, dilated ventricles, and an incomplete corpus callosum. In one of these patients, the magnetic resonance imaging pattern prompted molecular diagnostic testing when enzymatic testing was normal. We underscore that this constellation of features, which may be misdiagnosed as periventricular leukomalacia, illustrates a pattern highly suggestive of a deficiency of pyruvate dehydrogenase E1 alpha in female patients and should trigger appropriate diagnostic investigations.