Osteomalacia in a patient with severe anorexia nervosa

A 27-year-old woman with anorexia nervosa since adolescence was referred to our unit for generalized bone pain most severe at the pelvis and an inability to stand. She reported a pelvic fracture diagnosed one year earlier, which had failed to heal. Laboratory tests showed low serum phosphate, normal total serum calcium corrected for serum albumin, and very low urinary calcium excretion. Serum bone alkaline phosphatase and parathyroid hormone levels were elevated, whereas 25-hydroxy-vitamin D was severely decreased. Multiple vertebral and rib fractures were seen on plain radiographs. Radiographic images consistent with osteomalacia were pseudofractures of the left inferior pubic ramus, a bilateral complete fracture of the superior pubic ramus, and a characteristic pseudofracture (Looser zone) in the lateral margin of the right scapula. Vitamin D-deficient osteomalacia with secondary hyperparathyroidism was strongly suspected at this point, but it was decided not to confirm this diagnosis by bone biopsy with histomorphometry and osteoid labeling because of the emotional instability of the patient. Dual-energy X-ray absorptiometry disclosed severe demineralization. After two months on calcium and vitamin D supplements, the bone pain had abated and the patient was able to stand. Serum calcium had increased; serum phosphate, 25-hydroxy-vitamin D, and parathyroid hormone had returned to normal, and the pseudofractures showed evidence of healing. Osteoporosis is a well-known complication of anorexia nervosa. This case shows that osteomalacia can also occur. Vitamin D status should be assessed in patients with long-standing severe anorexia nervosa.