Osteomalacia and osteoporosis.

OSTEOMALACIA and osteoporosis are still sometimes confused because both diseases lead to a deficiency of calcium which can be detected on radiographs of the skeleton. This lack of calcium is the only feature common to the two diseases which are in all other ways easily distinguishable. Osteomalacia Osteomalacia will be discussed first, because it is a clearly defined disease which can be cured. Osteomalacia is the result of an imbalance between the supply of and the demand for vitamin D. The following description of the disease is based on our experience of twenty-two patients with osteomalacia after gastrectomy; there is no evidence that the features vary with the cause of the disease. The clinical features are nearly specific; the common ones are bone pains and muscle weakness. The bone pains are generalized, often worse at night, and sometimes associated with tenderness of the bones. The bone pains have been mistakenly attributed to rheumatoid arthritis, osteoarthritis or even neurosis, and the diagnosis of osteomalacia may be delayed for years. The muscle weakness is most obvious in the muscle around the pelvis, and a common symptom is difficulty in climbing stairs and in sitting up in bed without the aid of the arms. The muscles may be wasted as well as weak but there is usually no evidence of neurological damage; the weakness is a symptom of a primary muscle disorder. The radiological signs of the disease may be no more than a generalized lack of calcium in the skeleton indistinguishable from that in osteoporosis. In addition, Looser's nodes are a radiological finding which is almost specific for osteomalacia. However, the nodes are not always present, and similar lesions arise in Paget's disease of bone, hyper-parathyroidism and thyrotoxicosis (Camp & McCullogh, 1941). Looser's nodes are also known as pseudofrac-tures because they look like fractures on the radiographs, but they are often painless. The common and constant biochemical change in osteomalacia is an increase in the alkaline phosphatase activity in the blood (SAP); there may also be a low serum phosphorus or a low serum calcium. Our experience with the biopsy of bone is that a large excess of uncalcified bone tissue (osteoid), which is the classic histological feature of osteo-malacia, is only found in patients with the other typical features of the disease, in particular the clinical ones (Morgan et al., 1967a). Whether or not more subtle histological techniques will detect earlier …