Two unrelated children presenting with episodic isolated peripheral weakness were found to have pyruvate dehydrogenase (PDH) deficiency (OMIM 312170) due to previously undescribed mutations (Pro250Thr, Arg88Cys) in the gene for the E1alpha subunit (PDHA1). Taken in context with the literature, these patients suggest that acute weakness initially resembling Guillain-Barré syndrome is a potentially reversible and probably underdiagnosed manifestation of PDH deficiency and that peripheral nerve function should be evaluated in PDH-deficient patients.