PHYTOSTEROLAEMIA IN 3 UNRELATED SOUTH-AFRICAN FAMILIES

Phytosterolaemia (beta(-)sitosterolaemia), a rare, autosomal recessive disorder, has not hitherto been reported in Southern Africa. We repor t four new homozygous patients, from three unrelated families with sig nificant beta-sitosterolaemia (6.6-11.3%), campesterolaemia (2.2-4.6%) and clearly detectable, though unquantified, levels of cholestanol. T hree of the four patients had characteristic cutaneous and tendinous x anthomas within the first decade of life. The fourth patient, a 5 year old, was free of xanthomas despite persistently elevated concentratio ns of plant sterols in her plasma. Ail our patients were female bringi ng the male:female ratio in reported cases to 8:23. All were at or bel ow the 50th percentile for height and weight, and presented at some st age with borderline, hypochromic anaemia associated with red cell abno rmalities and thrombocytopaenia. The oldest patient showed suggestive clinical evidence of atherosclerosis affecting her aorta, ileofemoral bifurcation and possibly coronary arteries. All homozygotes responded to a diet restricted in phytosterols and the administration of cholest yramine with falls in plasma sterols of up to 68%.The recent discovery of a possible inherited defect in the synthesis of HMG CoA reductase in patients with phytosterolaemia makes this disorder a model system f or studying the biological role of this enzyme in regulating the absor ption and clearance of sterols other than cholesterol, and the factors governing the sterol composition of cell membranes.