Osteomalacia and osteoporosis in a woman with ankylosing spondylitis

Three months postpartum, a 33-year-old woman with ankylosing spondylitis (AS) suffered multiple vertebral fractures. Bone mineral density was 61-67% of age-matched normal values at the lumbar spine and proximal femur, and an initial iliac crest bone biopsy revealed osteoporosis and osteomalacia. Secondary causes of bone disease were excluded, and the patient was treated with calcium, vitamin D, and nasal spray calcitonin (400 u/day). Over 4 years, she has shown partial recovery of bone mass and almost complete resolution of osteomalacia. Osteoporosis and fracture occur in patients with AS, yet this case represents a rare association between AS and both osteomalacia and postpregnancy spinal osteoporosis.