Early-onset parkinsonism in a pedigree with phosphoglycerate kinase deficiency and a heterozygous carrier: do PGK-1 mutations contribute to vulnerability to parkinsonism?

Phosphoglycerate kinase 1 (PGK-1) is a glycolytic enzyme encoded by PGK-1, which maps to the X chromosome. PGK-1 deficiency causes X-linked recessive hereditary chronic hemolytic anemia, myopathy, and neurological disorders due to insufficient ATP regeneration. Early-onset parkinsonism has occasionally been reported as a neurological complication of this condition. However, heterozygous carriers of PGK-1 deficiency were thought to be neurologically asymptomatic. Here, we report a boy with PGK-1 deficiency and his mother, a carrier of a heterozygous mutation in PGK-1, both of whom presented with early-onset parkinsonism. The boy developed parkinsonism at 9 years of age. His parkinsonism partially responded to levodopa treatment. 123l-metaiodobenzylguanidine (MIBG) uptake was normal. His mother, who exhibited normal PGK-1 activity in erythrocytes, developed parkinsonism at 36 years of age. Her symptoms were undistinguishable from those of Parkinson’s disease (PD), despite her normal uptake of MIBG. Neither a point mutation in nor multiplication of SNCA was found. Additionally, hotspots of LRRK2 and GBA were not mutated. To our knowledge, this report provides the first description of parkinsonism in a carrier of PGK-1 deficiency. Interestingly, PGK-1 is located within the confirmed susceptibility locus for PD known as PARK12. These observations suggest that PGK-1 mutations confer susceptibility to PD. Mutations in the gene encoding phosphoglycerate kinase 1 (PGK-1) may confer susceptibility to early-onset Parkinson’s disease (PD). PGK-1 is a crucial protein for the breakdown of sugar in the body and mutations that cause PGK-1 deficiency lead to an X-linked metabolic disorder characterised by the breakdown of red blood cells, muscle weakness and various central nervous system abnormalities. Takashi Kasai at Kyoto Prefectural University of Medicine, Japan, and colleagues describe early-onset PD symptoms in a 9 year old boy with PGK-1 deficiency and his mother at 36 years of age. This is the first report of parkinsonism developing in an otherwise asymptomatic carrier of a PGK-1 mutation. The location of the PGK-1 gene on the X chromosome is within a confirmed susceptibility region for PD known as PARK12, suggesting that PGK-1 may directly contribute to the disease.