Avascular necrosis of bone and antiphospholipid antibodies in systemic lupus erythematosus.

Of a total of 800 patients with systemic lupus erythematosus, 37 were found to have developed avascular necrosis of bone (4.6%). Routine radiological screening of all joints was not performed and these 37 represented symptomatic patients only. Twenty-seven of these were positive for antiphospholipid antibodies (aPL) (73%). Both aPL positive and aPL negative patients had received large doses of oral steroids. The frequency of vasculitis and livedo reticularis, as well as arterial thrombosis was higher in the aPL positive group, but this did not reach statistical significance, perhaps because of the small numbers of patients involved. Although the difference in the frequency of thrombocytopenia was more marked in the aPL positive group (p < 0.08), once again, this was not statistically significant at the 5% level. Since the prevalence of aPL positivity in the general lupus population is about 30-40%, the presence of the aPL may be associated with an increased tendency to develop avascular necrosis. This is supported by recent reports of avascular necrosis occurring in patients with primary antiphospholipid syndrome in the absence of previous steroid administration.