osteomalacia

Osteomalacia is a condition characterized by defective mineralization of osteoid in mature bone, resulting in softened bones, bone pain, and muscle weakness. In adults it represents the metabolic bone disease counterpart of rickets, which affects growing children.

Causes and pathophysiology: The most common cause is vitamin D deficiency from inadequate intake, limited sun exposure, malabsorption, or liver/kidney disease that impairs vitamin D activation. Other causes include chronic kidney disease with reduced production of active vitamin D, phosphate-wasting disorders, and certain medications (such as anticonvulsants and glucocorticoids). Hypocalcemia and/or hypophosphatemia with secondary hyperparathyroidism may accompany osteomalacia.

Clinical features: Diffuse bone pain, tenderness, and proximal muscle weakness are common. Fractures, especially in the ribs, pelvis, spine, or long bones, may occur with minimal trauma. In children the condition is accompanied by rickets features, but in adults there are no growth plate abnormalities.

Diagnosis: Laboratory findings typically show elevated alkaline phosphatase; calcium and phosphate levels may be low or normal, with elevated parathyroid hormone. 25-hydroxyvitamin D is often low. Imaging may reveal osteopenia and pseudofractures (Looser zones); DEXA shows reduced bone mineral density. Bone biopsy shows unmineralized osteoid.

Treatment: Address the underlying cause and restore mineral metabolism. This usually includes vitamin D supplementation (ergocalciferol or cholecalciferol) with calcium if needed, and correction of phosphate disorders. In CKD or malabsorption, use of active vitamin D analogs and phosphate management may be indicated. Monitor labs and bone health and provide physical therapy as appropriate.