[The amyloidosis].

The clinical and pathological features of amyloidosis are examined in the light of a classification based on anatomical models of amyloid distribution: 1) generalised amyloidosis, including primary and secondary sporadic forms, hereditary and familial amyloidosis, and senile amyloidosis; 2) local amyloidosis, including amyloid tumours, neoplasia with amyloid stroma, and other forms. The nature of amyloid is described. Morphological, ultrastructural, biochemical and immunochemical research has shown that: 1) amyloid is a fibrillar protein with a typical EM and X-ray diffraction appearance; 2) two main types of amyloid proteins exist, one related to Ig light chains and found in primary forms and in association with myeloma, the other (called AA proteins) being the main component of secondary forms and certain types of familial amyloidosis; 3) serum proteins structurally related to the AA proteins may be used as amyloid precursors. The cause and mechanisms of amyloid production are becoming clearer. In particular, a relation with the production of Igs has been established. Improved methods for the diagnosis and treatment of the disease will throw more light and the nature of amyloid and its protein precursors.