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An 86-year-old woman was admitted having been found collapsed at home. On examination, she was pale, dehydrated, confused and disorientated with a rectal temperature of 28°C. There was no lymphadenopathy or bruising. Her pulse was regular at 50 beats/min and blood pressure was 150/100 mmHg. Cardiorespiratory, abdominal and neurological examinations were all unremarkable. Review of this patient's previous hospital notes revealed no significant illnesses in the past and she was on no regular medication. There was no history of excess alcohol intake. Social assessment revealed that she lived alone with inadequate heating provisions. Investigations showed thrombocytopenia, with a platelet count of 88 × 109/l (reference range 150–450 × 109/l), confirmed by analysis of two venous blood samples. Her haemoglobin was 14 g/dl, white blood count 8.2 × 109/l, with a normal differential count, and an erythrocyte sedimentation rate of 6 mm in the first hour. Serum urea was 11.1 mmol/l (3.5–8 mmol/l) with a serum creatinine of 127 μmol/l (50–105 μmol/l). Serum electrolytes, liver function tests, coagulation studies, electrocardiogram and chest X-ray were all normal, as were vitamin B12 and folate levels. Urine microscopy and culture revealed no evidence of urinary tract infection. Serum thyroid-stimulating hormone was 18.93 mU/l (0.5–5.0 mU/l ) and free thyroxine 14 pmol/l (9–24 pmol/l).
- What is the cause of thrombocytopenia?
- What complications may occur in this patient?
The potential causes of thrombocytopenia are numerous (box FB1). In this patient, the cause of thrombocytopenia was hypothermia. Following admission, she was rewarmed and rehydrated and the following day, her resting oral temperature had risen to 34°C and although she remained lethargic, she was no longer confused or disorientated. On day three her resting oral temperature was normal. On day nine, her platelet count had risen to normal (295 × 109/l).
Apart from the complications of thrombocytopenia, which include skin purpura, mucosal haemorrhage and prolonged bleeding after trauma, hypothermia may lead to other clinical features, shown in boxFB2.
Thrombocytopenia occurring with low body temperature was first described 58 years ago.1 Since then, animal studies have attempted to identify a cause for this phenomenon.2 3 In 1958, Villalobos used radioactively labeled platelets to demonstrate hepatic and splenic sequestration during hypothermia in dogs, with 80% of the platelets returning to the circulation on rewarming.2 A later study showed the liver to be the major site of sequestration.3 Disseminated intravascular coagulation and bone marrow failure have also been postulated as causes of hypothermia induced thrombocytopenia.
Platelet sequestration as a result of hypothermia is rare and only a few recorded cases exist.4 5 This was thought to be the cause of our patient's thrombocytopenia. She never exhibited any clinical features suggestive of disseminated intravascular coagulation and clotting studies were normal. Her initial full blood count did not show any evidence of bone marrow suppression and the rapid return of the platelet count to normal, mirroring the rise in body temperature, would suggest a causal relationship.
Although our patient experienced no problems as a result of her low platelet count, this case illustrates that thrombocytopenia is a potentially serious complication of hypothermia.