Pyruvate dehydrogenase (PDH) deficiency is one of the most common mitochondrial disorders. Patients with this genetic condition have difficulty utilising carbohydrates to produce energy and develop a combination of problems including seizures, poor balance, developmental delay, disability and have a reduced life expectancy. As for most mitochondrial disorders there is a lack of effective treatments. It is essential to understand the mechanisms underlying the disease in order to identify new treatments, and to understand the natural history of disease in order to prepare for clinical trials. To date, a natural history study of PDH deficiency has not been undertaken in the UK.

The researchers aim to undertake the first natural history study of PDH deficiency in the UK, to describe the spectrum of symptoms, genetics, management and outcomes in both children and adult patients.

Inclusion Criteria:

1. Compatible clinical history AND

2a Enzymatic confirmation demonstrating reduced PDH activity in patient cells or muscle tissue OR

2b Confirmed pathogenic mutation in a gene associated with primary PDH deficiency (PDHA1, PDHB, PDHX, PDP1, DLAT) OR

2c First degree relative with a confirmed pathogenic mutation causing primary PDH deficiency

Exclusion Criteria:

Patients with 'secondary PDH deficiency' that is patients who meet criteria 1 and 2a but who have received a genetic diagnosis which confirms pathogenic variants in a gene not associated with primary PDH deficiency.

Children and Adults with a diagnosis of (primary) Pyruvate Dehydrogenase Deficiency who are recruited from the community via tertiary healthcare services