Low-grade parasitaemias and cold agglutinins in patients with hyper-reactive malarious splenomegaly and acute haemolysis.
A cluster of 16 cases of hyper-reactive malarious splenomegaly (HMS) with severe, acute haemolysis, from an isolated, Venezuelan, Yanomami population, was prospectively investigated. Nine (69%) of the 13 HMS sera investigated but only one (7%) of 14 control sera (P < 0.005) contained elevated titres (of at least 1:32) of complement-fixing IgM cold agglutinins (CA). The CA detected had specificity for both the I and i blood-group antigens (with a relative predominance of anti-I) and wide thermal stability. The mean reciprocal CA titre was much higher for the HMS sera than for the control samples (59.16 v. 2.28; P < 0.001). Indirect tests for antiglobulin were positive for two of the 13 HMS cases (but none of 14 controls) investigated; all of the direct tests for antiglobulin gave negative results. The seven HMS cases checked, using an assay based on a nested PCR which amplified species-specific ribosomal sequences from Plasmodium vivax or P. falciparum, each yielded the PCR product that indicated P. vivax infection. However, only six (25%) of the 24 control samples (collected, at the same time as the HMS samples, from asymptomatic adults from the same Yanomami population) were PCR-positive (P < 0.001). In some cases at least, the acute severe episodes of haemolysis occasionally seen in HMS appear to be associated with an auto-immune, cold-agglutinin-mediated response triggered by non-patent parasitaemias.
Torres
J R
JR
Instituto de Medicina Tropical, Sección de Enfermedades Infecciosas, Universidad Central de Venezuela, Apartado 47019, Caracas 1041-A, Venezuela.
Villegas
L
L
Perez
H
H
Suarez
L
L
Torres V
M A
MA
Campos
M
M
D000328:Adult; D000373:Agglutinins / Q000032:analysis*; D000818:Animals; D000913:Antibodies, Protozoan / Q000032:analysis; D001323:Autoantibodies / Q000032:analysis; D016000:Cluster Analysis; D003450:Cryoglobulins; D004196:Disease Outbreaks; D004591:Electrophoresis, Polyacrylamide Gel; D006461:Hemolysis / Q000276:immunology*; D006801:Humans; D007159:Immunologic Tests; D007199:Indians, South American; D008288:Malaria / Q000276:immunology* / Q000469:parasitology; D018512:Parasitemia / Q000453:epidemiology / Q000276:immunology*; D010963:Plasmodium falciparum / Q000276:immunology; D010966:Plasmodium vivax / Q000276:immunology; D016133:Polymerase Chain Reaction / Q000379:methods; D011446:Prospective Studies; D016053:RNA, Protozoan / Q000032:analysis; D013163:Splenomegaly / Q000453:epidemiology / Q000276:immunology* / Q000469:parasitology
D000373:Agglutinins; D000913:Antibodies, Protozoan; D001323:Autoantibodies; D003450:Cryoglobulins; D016053:RNA, Protozoan; C029443:cold agglutinins