A single-case report of an older woman with Parkinson's disease who developed unexplained hypothermia and altered consciousness that resolved with supportive rewarming and did not recur over two years.

Alerts clinicians to a rare, reversible thermoregulatory/autonomic complication of PD but provides minimal mechanistic or therapeutic information useful for Parkinson's drug discovery.

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by both motor and non-motor manifestations, including autonomic involvement. Severe thermoregulatory disturbances, such as hypothermia, are uncommon but clinically significant complications of PD. We report a case of hypothermia associated with impaired consciousness in an older woman with PD in the absence of overt cold exposure. A 78-year-old Japanese woman with PD was admitted with moderate-to-severe hypothermia and altered mental status despite living in a well-heated indoor environment during winter. Laboratory and imaging studies revealed no alternative causes of hypothermia. Supportive management with intravenous fluids and active external rewarming resulted in rapid clinical recovery, and no recurrence was observed during a two-year follow-up period. This case highlights hypothermia as a possible thermoregulatory complication in PD. Clinicians should be aware of this potentially reversible condition in patients with PD who present with acute neurological deterioration, even in the absence of obvious environmental risk factors.