CS and Parkinson disease: Histochemistry: 10/17 PD patients had minor morphological abnormalities, including: ragged‐red fibres (n = 3); intermyofibrillar abnormalities (n = 7); and lobulated fibres (n = 6). Compared with controls, PD had: no change CS or SDH activity, mitochondrial complex I activity reduced by 71% Dopa‐treated, 68% de novo, complex III activity reduced by 35% Dopa‐treated.