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A 52 year old woman presented to the emergency department with two hours of central chest pain. She had no past medical history of ischaemic heart disease, diabetes, or hypertension. She had a family history of ischaemic heart disease; her brother had a myocardial infarction when 50 years old. She was taking no medication.
She smoked 20 cigarettes per day and had a 38 pack year history. On examination she was found to have palmar striated xanthomas (fig 1) and she was found to have hypothyroid facies on general examination. Her systemic examination was normal. Electrocardiography revealed T-wave inversion in lateral leads. Serial troponin I measurements were <0.3 mmol/l (Bayer Centaur: normal <0.3 mmol/l). Her serum was lipaemic (fig 2). Lipid profile revealed a serum cholesterol of 14.2 mmol/l and triglyceride of 9.3 mmol/l. Thyroid function tests were consistent with hypothyroid state with a thyroid stimulating hormone concentration of 45 mU/l and free thyroxine of 7 pmol/l. A coronary angiogram revealed mild diffuse disease. She was diagnosed to have familial type III hyperlipoproteinaemia and primary hypothyroidism. She was started on statin therapy, thyroxine, and antianginal medication. One of her three children was found to have a raised serum cholesterol concentration.
Type III hyperlipoproteinaemia, also known as remnant hyperlipidaemia, dysbetalipoproteinaemia or “broad beta disease”, is a rare genetic dyslipoproteinaemia characterised by accumulation in the plasma of remnant lipoprotein particles. Affected individuals have a substantially increased cardiovascular risk. Palmar striated xanthomas and tuberoeruptive xanthomas, which may coalesce to form tuberous xanthomas, are pathognomonic of this condition. The majority of patients are homozygous for the apoprotein E2 variant, reducing binding of chylomicron remnants and intermediate density lipoprotein to hepatic apoprotein E and low density lipoprotein receptors respectively, and causing their accumulation. This genetic substrate alone is insufficient for the clinical expression of the disease. An additional inherited or acquired lipid disorder, for example hypothyroidism as in this case, is required (1% of the population have the apo E2/E2 genotypes, but only 0.01% have type III hyperlipidaemia).