Recognizing the musculoskeletal manifestations of vitamin D deficiency ANDREA N. JONES and KAREN E. HANSEN, MD Ms Jones is a first-year medical student at the University of Wisconsin School of Medicine and Dr Hansen is assistant professor of medicine, division of rheumatology, department of medicine, at the University of Wisconsin School of Medicine and Public Health in Madison Abstract A disruption in any part of the vitamin D physiological pathway can result in vitamin D deficiency, which may lead to bone pain, muscle weakness, falls, low bone mass, and fractures. Recognizing the signs and symptoms helps physicians make a proper diagnosis and prescribe appropriate treatment. Physicians should suspect osteomalacia in patients who have prolonged vitamin D deficiency, a low serum calcium level, or a low serum phosphorus level. Patients with cystic fibrosis are at increased risk for deficiencies in fat-soluble vitamins, including vitamin D. Secondary hyperparathyroidism can develop in patients with chronic kidney disease as a result of low 25-hydroxyvitamin D levels or impaired conversion to 1,25-dihydroxyvitamin D. Patients may experience abnormal vitamin D metabolism as a result of taking anticonvulsants and other medications. Persons obtain vitamin D through ultraviolet light-induced skin synthesis and ingestion of vitamin D–rich foods. 1 The liver subsequently hydroxylates vitamin D to the storage form, 25-hydroxyvitamin D (25[OH]D), which undergoes another hydroxylation step in the kidney to become the bioactive form, 1,25-dihydroxyvitamin D (1,25[OH] 2 D). Regulated by parathyroid hormone (PTH), 1,25(OH) 2 D increases intestinal calcium absorption and is thought to affect bone metabolism and muscle function. A disruption in any part of the physiological pathway may result in hypovitaminosis D, or vitamin D deficiency. Vitamin D status influences musculoskeletal health. 1 Low vitamin D levels may lead to clinical manifestations, including bone pain, muscle weakness, falls, low bone mass, and fractures, with subsequent diagnoses of osteomalacia, osteoporosis, and myopathy. Physicians, especially rheumatologists, often encounter patients who have signs and symptoms of vitamin D deficiency, and recognizing them helps in making a proper diagnosis and prescribing appropriate treatment. In this article, we describe 5 patients with hypovitaminosis D who demonstrate various signs and symptoms to highlight diagnosis and treatment challenges. BACKGROUND The National Center for Health Statistics conducts annual surveys to evaluate the health and nutritional status of the American civilian population. In the National Health and Nutrition Examination Survey conducted from 2001 through 2004, about 76% of 11,009 Americans 20 years or older had vitamin D insufficiency, defined as a serum 25(OH)D level lower than 30 ng/mL. 2 Vitamin D deficiency, defined as a 25(OH)D level lower than 15 ng/mL, was present in 10% of adult men and 17% of adult women. 2 Risk factors for hypovitaminosis D include decreased sun exposure, increased age, increased skin pigment, malabsorption, and NIH Public Access Author Manuscript J Musculoskelet Med. Author manuscript; available in PMC 2011 October 6. Published in final edited form as: J Musculoskelet Med. 2009 October ; 26(10): 389–396. NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript