Abstract

Introduction Over 60 years ago Caplan's syndrome was described in the coal miners of South Wales (UK). Higher rates are seen in mining populations globally, particularly in kaolin workers. We describe Caplan's syndrome in a kaolin worker associated with a raised urinary cadmium level. Case report A 65-year-old Cornish kaolin worker with life limiting nodular erosive Rheumatoid Arthritis (RA) developed extra-articular manifestations including pulmonary nodules suggestive of Caplan's syndrome. Urinary cadmium was raised at 0.66 μmol/mol creatinine (UK male median 0.16 μmol/mol creatinine), 20 years post-industrial exposure cessation. Results Caplan's syndrome prevalence in kaolin workers is the highest of any occupation ever reported. Extremely elevated cadmium levels of 11.2-15.9 mg/kg have been observed in kaolin, fifty-fold higher than those reported in coal. Coal contains variable amounts of clays and minerals such as kaolinite, which determine cadmium content. We suggest that the kaolinite mineral capacity for adsorption of heavy metals, in particular cadmium, explains the scale and pattern of Caplan's syndrome prevalence seen in global mining populations, and further explains the pronounced interaction seen in sequential dust exposure and cadmium laden cigarette smoke.

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