Serum Phosphatase Activity in Seventeen Cases of Osteoporosis Circumscripta of the Skull

Abstract

The term osteoporosis circumscripta was introduced by Schüller 1 to describe a peculiar affection of the skull characterized radiographically by a marked decrease in density of large areas of the calvarium, the borders of the affected areas being irregular but sharply demarcated from the contiguous normal bone. The decrease in bone density in these cases is not due to bone destruction but rather to a localized osteoporosis, as post-mortem studies have shown. 2 , 3 , 4 It would appear that osteoporosis circumscripta of the skull, as defined roentgenographically, is identical with the abnormality of the skull described pathologically by Schmorl 5 as “hemorrhagic infarction of the bone.” 6 The disease is quite distinct, however, and readily differentiated from xanthomatosis, cholesteatoma, multiple myeloma, metastatic neoplasm, and the like.

Osteoporosis circumscripta is of particular interest because, despite the dissimilarity in gross morphology, it appears to be closely related to Paget's disease. The majority of cases described thus far have also had typical Paget lesions in the skull or elsewhere in the skeleton. Where osteoporosis circumscripta was the only abnormality in the skull, follow-up studies in several instances have revealed the development of “cotton-wool” lesions typical of Paget's disease within 3 to 10 years. Most observers in the field have concluded that osteoporosis circumscripta is, in fact, a form of Paget's disease, probably an early, predominantly osteolytic phase initiating the more familiar stage of excessive bone formation. 2 , 7 , 8 , 9

Whether or not this is an over-simplified view of the matter, as might be inferred from Schmorl's observations, 5 , 10 it seemed desirable to investigate the serum phosphatase activity in this disease.