Secondary
amyloid A (
AA) amyloidosis, which is a disorder of protein conformation and metabolism, is an important serious complication of inflammatory diseases, especially
rheumatoid arthritis (RA).
AA amyloidosis develops when AA fibrils, which are derived from the
acute-phase reactant, serum
amyloid AA (SAA)
protein, in the circulation, are deposited in organs and cause systemic organ dysfunction.
Caplan's syndrome, or rheumatoid
pneumoconiosis, is a rare type of
lung disease in which individuals suffering from RA develop lung nodules that are associated with occupational exposure to
silica and
coal dust. Confirmation of diagnosing as
Caplan's syndrome requires the patient's occupational history, imaging studies, and serology. A 72-year-old male, working as a tunnel construction worker for 38 years, with RA who had both chronic cardiac and renal dysfunction was referred to our hospital. He received a diagnosis of
pneumoconiosis about 20 years ago, after which he was also diagnosed with RA. So far we performed medical English literature searches on the combination of
Caplan's syndrome with
AA amyloidosis; there were no articles in relation to such association. Although RA is one of the most common underlying diseases that occur with
AA amyloidosis, our report here is the first description of a case of
Caplan's syndrome associated with
AA amyloidosis. In this report, we provide details about this
rare disease occurring with
AA amyloidosis and discuss on the possible pathogenesis of
AA amyloidosis from a genetic point of aetiological view.