College Answer

a) The most likely diagnosis is Myxoedema coma /severe hypothyroid coma. The normal CT brain excludes a significant organic brain pathology, and normal ammonia + normal hepatic enzymes make hepatic encephalopathy less likely. The clinical picture in concert with the features of a low Na, low glucose, high cholesterol, a pericardial effusion and the history of thyroxine supplementation is highly suggestive of hypothyroidism. Marks were also allocated if a reasonable alternative diagnosis was given, provided that this was accompanied by a rational justification.

b) Many precipitating factors could be present, but consider: sepsis, drugs (eg. betablockers, amiodarone), stroke, and a patient non-compliant with therapy.

Sixteen out of twenty-six candidates passed this question.

Discussion

The history is characteristic of myxoedema coma, which is discussed in greater detail elsewhere

In addition to the background of hypothyroidism, the patient has the trifecta of features:

• cardiovascular collapse
• hypothermia
• decreased level of consciousness

The associated features of pericardial effusion and hyponatremia complete the classical picture.

The college have not given you the puffy face and non-pitting oedema, but they are hardly necessary.

Also, the history of cirrhosis is given, and the patient does have a "flap", but it is probably not a flap of hepatic encephalopathy, but of hypercapnea, which is associated with myxoedema coma. The ammonium level is 41, which (though not related to the severity of encephalopathy) is not sufficiently abnormal to cause concern.

As for the precipitating factors... Surely, the osteomyelitis itself might cause the myxoedematous decompensation, but the clever college examiners have probably thrown this in because they know that osteomyelitis of this sort tends to be treated with rifampicin, and rifampicin tends to increase the rate of hepatic clearance of thyroxine.