Teaching Case

Here, we describe the clinical case of a patient affected by a particular form of bone dysplasia, previously diagnosed as progressive diaphyseal dysplasia or Camurati-Engelmann's disease. Our patient presented bilateral localization of diaphyseal dysplasia, cortical thickening in the anterior tibiae and in the lower third of radium and ulna, Raynaud phenomenon and increased serum alkaline phosphatase activity. On the basis of these findings, we tend towards the diagnosis of Ribbing's disease, and we hypothesize that this last disorder can be considered as a variant of Camurati-Engelmann's disease, with the absence of systemic involvement and the onset in adulthood.

A 41-yr-old man, diagnosed as affected by Camurati-Engelmann's disease 15 years earlier, was admitted to the hospital in September 1999 with worsening bilateral leg pain and the onset of Raynaud's phenomenon . His parents, two sisters and two brothers, were both alive and in good health. His medical history was unremarkable. At admission, his physical examination showed tenderness and slight warmth over the tibial anterior aspects , and no-inflammatory oedema of the hands. The remaining clinical examination was normal. Chemistry profile showed an increase of alkaline phosphatase activity ( 21.96 UKA, nv: 5-14 UKA), of the total urinary hydroxyproline ( THP) ( 33 mg/24 hrs/mq , n.v. : 6-22 mg/ 24 hrs/ mq ) and of ESR ( 31 mm/1st hour, n.v.: < 20 mm/1st hour). The immunological parameters (serum immunoglobulins, total complement and its fractions, circulating immune-complexes, T and B lymphocytes ) were in normal range. The antinuclear antibodies were absent, the antiphospholipid and anticardiolipin antibodies were in normal limits. Systemic skeletal X-ray showed a characteristic area of patchy thickening of the periosteal and endosteal surface of both the tibial diaphyses (fig. 1a, 2a) and of the lower third of radium and ulna ( fig.3a). A bone scintigraphy revealed a light increased radionuclide accumulation at the same levels. Plethysmography and electromyography of the legs were normal, while plethysmography of the hands showed a significant slowing down in the blood flow , as confirmed also by the microscopical examination of the nail-fold capillaries. An abdominal ultrasonography excluded hepatosplenomegaly. The patient was treated with glucocorticoids in small doses ( 6- metilprednisolone, 8 mg daily) for two weeks, because of the inefficacy of the therapy with nonsteroidal anti-inflammatory drugs, administrated before his hospitalization. Rapidly, leg pain improved; also the oedema of the hands decreased significantly. Among the biochemical parameters, only ESR appeared significantly reduced ( 18 mm/1st hour) two weeks after the start of corticosteroids. He was discharged in good health, under chronic treatment with alendronate (10 mg daily). The patient has been constantly controlled ( the last clinical, laboratory and instrumental examinations have been performed on 17 August 2000 ) : he has never shown any relapse of the leg pain. Serum phosphatase activity, THP and ESR appeared in normal range. The radiological bone lesions appeared unchanged and the bone scanning appeared normal. Figures Fig. 1a. X-ray of the left tibia: evidence of cortical thickening of the tibial diaphysis. Fig. 2a. X-ray of the right tibia: evidence of cortical thickening of the tibial diaphysis. Fig. 3a. X-ray of the forearms: evidence of bilateral, cortical thickening in the lower third of the radium and ulna.

In 1949, Ribbing (1)described four siblings with diaphyseal sclerosis of the femora and tibiae, which was not always symmetric. He observed that his cases differed in several ways from the reported cases of Camurati-Engelmann's disease(2), and he concluded that the examined four siblings were affected by a separate pathological entity, termed " hereditary multiple diaphyseal sclerosis"(1). Further studies demonstrated that Camurati-Engelmann's disease has an autosomal dominant mode of inheritance, while Ribbing's disease an autosomal recessive mode of inheritance. Our patient is a sporadic case: so we are not able to characterize his pattern of inheritance. Our patient shows : Raynaud's phenomenon; bilateral localization of diaphyseal dysplasia in both the tibiae, radii and ulnae ; focally light increased radionuclide accumulation in the above-mentioned areas; increase of serum alkaline phosphatase activity, of THP and of ESR. Many aspects of the presented case suggest the diagnosis of Ribbing's disease : in particular, the presentation after puberty without gait and neurological abnormalities, and the less extensive skeletal involvement. On the contrary, the presence of Raynaud's phenomenon and the increase of ESR, alkaline phosphatase activity and THP more closely recall Camurati-Engelmann's disease. Moreover, some authors affirm that a moderate increase in bone turnover biochemical markers is not peculiar to Camurati-Engelmann's disease (3). Furthermore, some authors report that the bone lesions of Ribbing' s disease can be either unilateral or bilateral (4). Lastly, the symptomatic treatment with corticosteroids (5) and bisphosphonates , considered as disease-modifying drugs , are shown effective in both the disorders by the above-mentioned authors and also by us. Consequently, the therapeutic approach, similar in both the two conditions, does not help us to differentiate the two pathological events. Therefore, many researchers affirm that Ribbing's disease can be considered as a variant or an adult form of Camurati-Engelmann's disease also because sporadic cases of Camurati-Engelmann's disease do occur and mild clinical forms are transmitted as an autosomal dominant trait with variable expression (3). Our case wants to enrich the small data of literature and to support the opinion that Ribbing's disease differs from Camurati-Engelmann's disease, only for the absence of a systemic involvement and the onset in adulthood. Until now, we are not able to clarify if the different clinical patterns are due to the variable expression of the same disorder or depend on an unlike molecular mechanism . Further cases are required to remove doubts.