Osteochondritis (Calvé’s disease) of a vertebral body: a rare form of vertebra plana (T. Shisha et al.)

This case report raises an interesting discussion concerning the etiologies of vertebra plana, defined as a flattened vertebral destruction occurring most frequently in children between the ages of 3 and 15.

In 1925 Calvé [1] was the first to describe this radiologic finding in a 7-year-old boy. He used the term ‘osteoarthritis of the vertebral body’, the suffix “itis” evoking inflammation of bone and cartilage. However, Calvé suggested that it was possibly an aseptic necrosis of the vertebral body. In subsequent studies of the literature [2–4], it was demonstrated that vertebra plana was principally due to an eosinophilic granuloma, a separate entity of histiocytosis X, usually confined to bone. Solitary painful lesions are the most common findings, although they may be polyostotic but remaining different in their courses and prognosis from the two other entities of histiocytosis X (Letterer-Siwe disease and Hand–Shuller–Christian disease). Vertebra plana is a characteristic result of an isolated involvement of eosinophilic granuloma.

In this case report, imaging studies are strongly suggestive of eosinophilic granuloma with the progressive collapse of the anterior part of the vertebral body ultimately reduced to a slight hyperdense band, the posterior part of the vertebral body keeping some height. The benign clinical course, including complete disappearance of the symptoms, is also in keeping with the usually favorable prognosis of a solitary focus of eosinophilic granuloma. The authors of the case report state that they were able to rule out the diagnosis of eosinophilic granuloma, considering the absence of histiocytes and eosinophilic leucocytes on the biopsy. However, studies have shown that bone lesions of eosinophilic granuloma may heal and regress spontaneously with an ensuing disappearance of the characteristic histologic features. This was probably the case in the patient followed up by the authors of the case report, as the biopsy was carried out rather late in the evolution. Moreover, it should be noted that lymphocytes and plasmocytes discovered on the biopsy are part of the histologic features of eosinophilic granuloma. It has also been shown that partial reconstitution of vertebra plana can be part of the healing process. Radiologic follow-up of the destructed vertebra would be extremely instructive.

Definition of terms is certainly essential. Vertebra plana is an imaging entity. Partial destruction and flattening of a vertebral body in a child may be due to various causes, including, for example, lymphoma, neuroblastoma, Ewing’s sarcoma, aneurysmal bone cyst among other benign or malign conditions, calling for a biopsy, especially in doubtful cases.

In this case report it would be more appropriate to conclude that the diagnosis remains doubtful, although eosinophilic granuloma appears highly probable. Neither Calvé nor the authors of the case report have demonstrated that osteochondritis of the vertebral body (aseptic necrosis?) can be added to the list of etiologies of vertebra plana as a separate entity.