Antineutrophil cytoplasmic antibody (
ANCA) is often used in the laboratory to confirm paucicellular
vasculitis like
Wegener's granulomatosis,
Churg Strauss syndrome or
polyarteritis nodosa in the presence of suggestive clinical features. In tropical countries,
tuberculosis,
leprosy and, occasionally,
malaria can produce clinical features similar to a vasculitic illness and all the three
infections are known to be associated with auto
antibodies. We tested 318 patients suffering from
malaria,
tuberculosis or
leprosy for
ANCA positivity.
ANCA positivity was found in 19%, 32% and 30% of
malaria,
tuberculosis and
leprosy patients (Pradhan V, Badakere S, Shankarkumar V, Iyer Y, Ghosh K, Karnad D, Indian J Malariol, 39:51-59, 2002; Pradhan V, Badakere S, Ghosh K, Pawar A, Indian J Med Sci, 58:283-288, 2004a; Pradhan V, Badakere S, Shankarkumar V, Lepr Rev, 75:50-56, 2004b), respectively, raising the possibility that
ANCA positivity with clinical features suggestive of
vasculitis in tropical countries may even be related to the background noise of this seropositivity caused by one of these three
infections rather than confirming the diagnosis of paucicellular
vasculitis. Hence, one should be careful about the background noise of
ANCA positivity caused by these
infections while diagnosing a vasculitic illness.