Benign osteoblastoma as a cause of osteomalacia. A report of two cases.

Two patients, a Japanese man and woman both aged eighteen, developed symptoms and signs of osteomalacia over a period of five years. Each of them had a benign osteoblastoma, one in the right fourth metacarpal and the other in the uppermost third of the right humerus. Resection of the tumours without any treatment by vitamin D resulted in rapid cure of the osteomalacia. Attempts to prove a phosphaturic humoral substance or vitamin D antagonist in the osteoblastoma of the humerus were unsuccessful, probably due to prompt excretion from the tumour cells.