Osteomalacia—what the rheumatologist needs to know

Osteomalacia is a metabolic bone disease frequently seen by rheumatologists. The primary defect in this disorder lies in inadequate mineralization of normally formed osteoid leading to soft bones, which are easily deformed. The common cause is vitamin D deficiency due to inadequate exposure to sunlight, malabsorption, intake of drugs like phenytoin and chronic renal and hepatic disease. The exact prevalence of this disease is not known. However, vitamin D deficiency has been shown to be extremely common in Indians. Certain groups like adolescents, elderly, pregnant and lactating women and those confined indoors, are more prone to develop osteomalacia. Osteomalacia usually presents with generalized bone pain, proximal muscle weakness and non-specific constitutional features. It is often confused with hypothyroidism, inflammatory myopathies, multiple myeloma and even arthritis. The gold standard of diagnosis, bone biopsy, is rarely performed. Diagnosis rests on a combination of clinical, laboratory (elevated alkaline phosphatase, low serum calcium) and radiological findings (diffuse demineralization, Looser's zones). With early institution of treatment with vitamin D and calcium, most patients recover in 3–6 months. Diet is a very poor source of vitamin D. Increased exposure to sunlight and supplementation of vitamin D in susceptible populations are important measures to prevent osteomalacia.