Manifestations ostéoarticulaires des amyloses

Abstract: Amyloidosis is defined by the extracellular deposit of proteins which share common tinctorial affinities, a fibril aspect under electron microscopy and spatial conformation called beta pleated. Significant progress has been made in gaining an insight into the clinical, biochemical and genetic characteristics of amyloidosis. Once regarded a mere overload disease, it is currently considered as a disease of misfolded proteins. Indeed it is certain that abnormalities of spatial pattern play an essential role in the responsibility for the pathology of many proteins whose amyloid fiber is the final common way. The mechanisms of fibril formation remain poorly understood. They involve both changes in the conformation of proteins and other major in vivo interactions between amyloid protein and the extracellular matrix. In most cases amyloidosis represents the bulk of histopathological lesions and its pathogenic role is certain. In other cases it is only one elementary lesion of the disease and its role is controversial. The amyloidosis responsible for osteoarticular manifestations are the AL immunoglobulin amyloidosis, the beta2-microglobulin amyloidosis in patients under haemodialysis and finally the amyloidosis of transthyretin in its genetic and senile forms. Rheumatological manifestations of immunoglobulin amyloidosis are numerous and important to know because often indicative of the disease. Deposits affect joint and periarticular structures. The most common sign and symptom that should raise questions is a progressively developing bilateral symmetric polyarthritis with negative immunology and absent specific structural abnormalities. Carpal tunnel syndrome is also very common and should suggest the etiology. Other clinical representations are rarer and can be expressed by an isolated bone tumour (amyloidoma) or integrating in a form of systemic AL amyloidosis. The beta2-microglobulin amyloidosis occurs in patients treated by chronic haemodialysis. It is responsible for carpal tunnel syndrome, chronic arthralgia, and above all a specific destructive spondyloarthropathy. Finally the transthyretin amyloidosis can also cause carpal tunnel syndrome. [Copyright &y& Elsevier]