Osteomalacia is a disease of the bones where there is an impaired mineralization of the bones. The poor mineralization of the bones is caused by a long-standing hypocalcemia and hypophosphatemia usually associated with chronic vitamin D deficiency. It is differentiated from rickets in that it is a disease of adults and not of children. In children the manifestations are slightly different due to the non-closure of the epiphyseal growth plates. (Robbins, 2009, pg. 433)
There are several causes of osteomalacia, the most important being the aforementioned vitamin D deficiency. However, chronic acidosis as in diabetes, renal disorders, disorders of vitamin D metabolism, various tumors, toxins, and genetic factors may also lead to the disease. Furthermore, chronic hypocalcemia, even in the absence of an underlying vitamin D deficiency may also lead to osteomalacia. (Harrison’s, 2008, pg. 2376).
Osteomalacia may be asymptomatic and simply appear as an incidental finding on an x-ray as osteopenia. A specific radiological finding in the disease is a pseudofracture, which is a radiolucent line where a part of the skeleton is in contact with a pulsating artery – these lines are common on the scapula, pelvis, and femoral neck (Harrison’s 2008, pg. 2376). Other symptoms of the disease include bone pain and muscular weakness, bone tenderness, fractures, difficulty walking, and muscle spasms and cramps (Robbins, 2009, pg. 436).
The prognosis of osteomalacia is also dependent on the underlying causes of the mineralization disorder. Nutritional osteomalacia has a relatively good prognosis; whereas a cancer associated osteomalacia will have a significantly worse prognosis. Often times the symptomology of the disease can be managed in the secondary cases of osteomalacia while treatment of the underlying condition will prove futile (Harrison’s, 2008, pg. 2376).
Treatment of the disease involves corrections of the vitamin D levels and the calcium levels in the patient. Furthermore, if the disease is a secondary manifestation, then the underlying condition should be treated too (i.e. correction of acid imbalance). Vitamin D and calcium supplements have a wide margin of safety, but overdoses can lead to toxicity that manifest as muscle cramping, cardiac symptoms, gastro-intestinal symptoms and renal stones.
The current state of clinical research indicates the importance of adequate calcium replenishment when administering vitamin D supplementation. (Lafage-Proust, et al., 2013). Inadequate calcium intake even while taking vitamin D supplementation may not truly treat the pathology and in its absence may lead to more pathological fractures and not corrects the bone densities.
In sum, there are a wide variety of causes of osteomalacia with the most important being inadequate vitamin D intake in the elderly, or inadequate sunlight exposure in hospital bound or African-American patients. If vitamin D intake is the root of the problem, it is relatively easy to correct, however underlying pathologies such as cancer and diabetes make treatment and prognosis much more difficult. Treatment generally involves nutritional supplementation that is well tolerated.
References:
Bringhurst, F.R., Demay, M.B., Krane, S.M., Kronenberg, H.M. (2008). Bone and Mineral Metabolism in Health and Disease. In S. Fauci, D. Kasper, D. Longo, E. Braunwald, S. Hauser, J.L. Jameson, & J. Loscalzo (Eds.), Harrison’s Principles of Internal Medicine (17th ed.) (pp. 2365-2415). New York: McGraw Hill Medical
Kumar, V., Abbas, A.K., Aster, J.C., Fausto, N. (2009). Environmental and Nutritional Diseases. Robbins and Cotran Pathologic Basis of Disease (8th ed.) (pp. 399-446). New York: Saunder’s
Harris, S. (2006). Vitamin D and African Americans. The Journal of Nutrition, 136, 1126-1129
Lafage-Proust, et al. (2013). High Bone Turnover Persisting after Vitamin D Repletion: Beware of Calcium Deficiency. Osteoporosis International. DOI 10.1007/s00198-013-2273-1
