Hyperparathyroidism, long recognized as osteitis fibrosa cystica of von Recklinghausen, has become a well recognized clinical entity. Through the researches of such investigators as Hunter1and Jaffe,2stimulated by the observations of Mandl,3and from the numerous reports that have been published, the usual manifestations of this disease are now common knowledge to the clinician. The onset of the condition is insidious, and the symptomatology is so vague that until recently in most instances the patient with hyperparathyroidism has gone with the condition undiagnosed for many years. The clinical diagnosis is made, as a rule, only after the development of bony deformities or pathologic fractures. The case presented here is no exception to the rule, but because of certain unusual features it seems worthy of being reported. The unusual features in this case were the associated hyperthyroidism, the rapid development of the clinical picture and the almost