Secondary amyloidosis and the serum amyloid precursor in leprosy: geographical variation and association with leukocytosis.

The prevalence of the amyloid-related serum component, protein SAA, was investigated in two groups of leprosy patients from different areas of Papua New Guinea. Protein SAA was more prevalent in coastal leprosy patients (49% positive) than in highland patients (21% positive). Paradoxically, many more cases of amyloidosis were diagnosed in the highland group (17 of 199) than in the coastal group (3 of 112). In the highland patient group, SAA was found to correlate with the leprosy disease spectrum, being more prevalent in patients toward the lepromatous pole. Borderline and tuberculoid patients who had detectable SAA usually had neurotrophic ulcers. No such relationships were observed in the coastal patient group, probably because other infections, more common on the coast, were also responsible for causing increased concentrations of SAA which is known to behave as an acute phase reactant. A correlation was observed between SAA positivity and neutrophil leukocytosis. This suggests that various inflammatory stimuli such as erythema nodosum leprosum reactions, neurotrophic ulcers and intercurrent infections, all contribute to the prevalence of SAA in leprosy patients.