• seborrhoeic dermatitis;
  • parkinsonism;
  • Pityrosporum ovale;
  • pathogenesis

The spouses of a group of aged sufferers have been demonstrated to have multifarious differences relevant to parkinsonism from matched controls, which were difficult to explain by selective mating, learned or reactive behaviour. Could parkinsonism be transmissable? The frequency of inflammation and scaling on head or neck was greater (P = 0.05) in these spouses (19 available) than in controls (36), the best discriminating site of inflammation being scalp (P = 0.02). Both seborrhoeic dermatitis and overt, or pre-clinical, parkinsonism occurred in sufferers and spouses: to presume they are not causally related is to accept multiple entities. In favour of seborrhoeic dermatitis being causal for parkinsonism, rather than vice versa, is the involvement of a known organism, Pityrosporum ovale, in the dermatitis, and that the evidence of parkinsonism in the spouses indicated that they were only part way down the path towards the clinical condition.