Seasonal Thrombocytopenia Induced by Hypothalamic Hypothermia: A Case Report

Background The hypothalamus plays a central role in thermoregulation. In brain tumors involving the hypothalamus, hypothermia can lead to rare but serious complications such as impaired consciousness and thrombocytopenia. Case Presentation An 80-year-old man was brought to our hospital in February after being found unresponsive in his bedroom. He had a history of surgery for a giant PitNET at another institution and was subsequently followed at our hospital. Having declined further surgical intervention, he was managed conservatively. During follow-up, episodes of unexplained paroxysmal thrombocytopenia were occasionally observed. Upon arrival, he was comatose with a core body temperature of 32.1°C. Laboratory tests revealed marked thrombocytopenia (55,000/µL) and widespread subcutaneous hemorrhages. Hypothermia was considered the primary cause of the impaired consciousness. Because the patient’s body temperature was gradually normalized by external warming, his level of consciousness improved, and his platelet count also began to recover over the following days. A retrospective review of prior laboratory data revealed a seasonal pattern in the thrombocytopenia. Based on these findings, the thrombocytopenia was considered secondary to hypothalamic hypothermia. Conclusions Hypothalamic tumors can precipitate hypothermia and seasonal hematologic disturbances. In patients with brain tumors presenting with unexplained, seasonal, or periodic thrombocytopenia, underlying thermoregulatory dysfunction due to hypothalamic involvement should be considered.