Several forms of xanthomata give important clinical clues to the nature of the underlying pathophysiological defect. Thus, tendon xanthomata typically occur in familial hypercholesterolaemia and in familial defective apo B. Their presence in the Achilles tendons or the extensor tendons of the hand (Fig. 6.19) is pathognomonic of genetic defects in interactions of LDL with its receptor. Occasionally, xanthomata are seen on the patellar tendon. Since xanthomata are often subtle, careful examination of these sites is required for their detection.
