A case of crippling osteoporosis with muscular weakness, hypophosphatemia, hyperparathyroidism, defective skeletal calcification and cartilage destruction is reported. The patient, a male was observed from the age of 2 1/2 until his death at the age of 33 years. This bone/cartilage disease failed to respond to phosphate supplementation, parathyroidectomy and calcitriol. We believe this may represent a hitherto undescribed entity.