We screened for PDHA1 mutations in 40 patients with biochemically demonstrated PDHc deficiency or strong clinical suspicion, and found changes with probable pathological significance in 20. Five patients presented new mutations: p.A169V, c.932_938del, c.1143_1144 ins24, c.1146_1159dup and c.510-30G> A, this latter is a new undescribed cause of exon 6 skipping. Another four mutations have been found, and previously reported, in our patients: p.H113D, p.P172L, p.Y243del and p.Y369Q. Eleven patients presented seven known mutations: p.R127Q, p.I166I, p.A198T, p.R263G, p.R302C, p.R378C and c.1142_1145dup. The latter three were found in more than one unrelated patient: p.R302C was detected in a heterozygous girl and a mosaic male, p.R378C in two males and finally, c.1142_1145dup in three females; only one in 20 mothers was found to be a carrier (p.R263G). Apart from those 20 patients, the only alteration detected in one girl with clear PDHc and PDH-E1 deficiency was the silent change c.396A> C (p.R132R), and other eight PDHc deficient patients carry combinations of known infrequent polymorphisms that are overrepresented among our 20 unsolved patients. The importance of these changes on PDH activity is unclear. Investigations in the other PDHc genes are in course in order to elucidate the genetic defect in the unresolved patients.