Vitamin D deficiency osteomalacia

**Definition:** Osteomalacia is a disorder of defective mineralization of newly formed osteoid at sites of bone turnover. Several different disorders cause osteomalacia via mechanisms that result in hypocalcaemia, hypophosphatemia, or direct inhibition of the mineralization process. Severe vitamin D deficiency, secondary to inadequate dietary intake, lack of sun exposure, gastric bypass or malabsorption (celiac disease), is the most common cause of osteomalacia in adults.

**Long definition:** Osteomalacia can also occur in patients with primary hypophosphatemia due to one of the hereditary hypophosphatemic rickets syndromes (eg, X-linked hypophosphatemic rickets, autosomal dominant hypophosphatemic rickets) or with tumor induced osteomalacia, an acquired paraneoplastic syndrome of renal phosphate wasting.