osteomalacie

Osteomalacie is a metabolic bone disease defined by defective mineralization of osteoid in mature bone, resulting in softened bones and bone pain. In children the analogous condition is rickets; osteomalacia denotes the adult form after epiphyseal closure.

Most cases are due to vitamin D deficiency from inadequate intake, malabsorption, liver disease, or insufficient sun exposure. Other causes include hypophosphatemia from renal phosphate wasting, chronic kidney disease with reduced calcitriol production, and medication effects (anticonvulsants, rifampin, corticosteroids).

Pathophysiology: osteoid is produced normally but mineral deposition of calcium and phosphate is impaired, leading to excess unmineralized osteoid, bone softening, and fragility. Secondary hyperparathyroidism may occur; alkaline phosphatase is usually elevated.

Clinical features: diffuse bone pain, especially in the pelvis, hips, thighs, and spine; proximal muscle weakness and a waddling gait; increased risk of insufficiency fractures. Children with vitamin D deficiency may present with rickets if still growing.

Diagnosis: laboratory findings typically show low or normal calcium, low or low-normal phosphate, elevated alkaline phosphatase, and elevated parathyroid hormone; 25-hydroxyvitamin D is reduced. Imaging may show osteopenia and Looser zones; bone density is reduced. Confirmation may require bone biopsy in unclear cases.

Treatment and prognosis: management targets underlying cause and vitamin D and calcium repletion. Vitamin D2/D3 and calcium supplementation are standard; in CKD or malabsorption, active vitamin D or calcitriol may be needed. With treatment, pain improves and fracture risk declines; radiographic changes may persist.