Osteomalacia is a distinctive disorder of adults with bone pain and muscle weakness. It is characterized histologically by broad seams of uncalcified bone matrix in sections of trabecular bone. It is distinct from osteoporosis which is generally asymptomatic before a fracture occurs. Histologically osteoporosis has no characteristic findings other than diminished bone quantity.
Osteomalacia, like rickets in children, has long been recognized as a consequence of vitamin D deficiency. That they were essentially the same disorder was first appreciated in the early 1900s, particularly as a result of studies of newborn infants with rickets whose mothers were then found to have severe unrecognized osteomalacia.
While the bone disorders, rickets and osteomalacia, are the most widely known consequences of vitamin D deficiency, research in recent years has suggested that the impact may be on many other organs. Low levels of 25- hydroxyvitamin D (25OHD), the principal metabolite of vitamin D in blood, have been associated with increased risk of type I diabetes mellitus, multiple sclerosis, cardiovascular disease and some forms of cancer. While these associations may reflect genuine causation, many of these studies fail to eliminate other possibilities. These include ‘reverse causation’ (the disease may cause low 25OHD levels by reducing sunlight exposure) and confounding (reduced physical activity may have similar results).We need to maintain an open mind in relation to the relevance of vitamin D deficiency to problems outside the skeleton.