Antiphospholipid antibodies, systemic lupus erythematosus, and non-traumatic metatarsal fractures

Stress fractures are common in military recruits and athletes and are thought to be secondary to stress and overuse. Less often they are associated with metabolic disorders such as osteoporosis, hypophosphataemia, and diabetes mellitus.

Analysis of 19 patients with systemic lupus erythematosus and antiphospholipid antibodies presenting consecutively with foot pain. All had metatarsal fractures (six bilateral) without any obvious history of trauma.

13 of the 19 patients had antiphospholipid syndrome. Among the whole group, 13 had normal bone mineral density, one had osteopenia, and five others had osteoporosis as defined by WHO criteria; 10 had received steroids, mostly in low dosage; 13 were receiving warfarin. There was no evidence that a metabolic bone abnormality was a unifying factor in the pathogenesis.

Atraumatic metatarsal stress fractures may occur in SLE, particularly in association with the antiphospholipid syndrome. The pathogenesis of these fractures remains uncertain but microinfarcts in the metatarsal bones are a possible cause.