Osteo-articular manifestations of amyloidosis.

Whether it is overload disease or mispleated proteins, amyloid is a great pretender. This is especially true for all of the osteo-articular manifestations of amyloid light chain (AL) amyloidosis, which may mimic rheumatoid arthritis, polymyalgia rheumatica, a myeloma or a bone tumour. To improve the prognosis, AL amyloidosis must be considered in front of atypical osteo-articular manifestations. Amyloidosis Ab2M of chronic haemodialysis (members' arthropathy and destructive spondylitis) is a specific entity that needs to be differentiated from other osteoarthropathies of chronic renal failure. It has become exceptional since the progress of haemodialysis. Finally transthyretin amyloidosis(ATTR) can be responsible for carpal tunnel syndrome(CTS) in its genetic and senile form. Although amyloidosis is rare, it represents one of the aetiologies of CSC, regardless of its type. In the specific context of haemodialysis, this poses no difficulty for the clinician. Yet AL amyloidosis must be considered more often, as must senile amyloidosis ATTR in the elderly. It seems obvious that the anatomo-pathologic analysis with specific staining with Congo red - see typing - should be systematically performed in the case of surgical neurolysis. 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. Once regarded as 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 fibre is the final common way. 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 osteo-articular manifestations are the AL immunoglobulin amyloidosis, the beta2-microglobulin amyloidosis in patients under haemodialysis and finally the amyloidosis of transthyretin (genetic and senile). Rheumatological manifestations of immunoglobulin amyloidosis are numerous and often indicative of the disease. Deposits affect joint and periarticular structures. The most common presentation is a progressively developing bilateral symmetric polyarthritis with negative immunology and absent specific structural abnormalities. Carpal tunnel syndrome (CTS) is very common and should suggest the aetiology. Other clinical representations are rarer as an isolated bone tumour (amyloidoma) or integrating systemic AL amyloidosis. β 2-Microglobulin amyloidosis occurs in patients under chronic haemodialysis. It is responsible for CTS, arthralgia and above all a specific destructive spondyloarthropathy. The transthyretin amyloidosis also causes CTS.