Poikilothermia in a 68-year-old female. A risk factor for accidental hypothermia, or hyperthermia.

A 68-year-old woman presented in wintertime in a cold climate with ataxia and numbness in her legs and was found to be profoundly hypothermic in hospital. No endocrine or neurological cause for hypothermia could be distinguished. Physiological investigation, including a sympathetic release test, exposure to gradually increasing environmental temperatures and prolonged exposure to a high temperature suggested she was at that time regulating her core temperature around a set value which was several degrees lower than normal. Metabolic rate was 42 per cent below the value predicted from standard tables. Further measurements over a one-month period in a warm climate suggested a poikilothermic temperature control mechanism, with a possible risk of environmental hyperthermia. No pathological basis for this disorder has yet been identified, but it is suggested that a small localized hypothalamic vascular event has occurred.