Investigations in the aetiology and pathophysiology of sago haemolytic disease

Sago haemolytic disease (SHD) is a suspected mycotoxocosis that causes acute and sometime fatal intravascular haemolysis and has only been described in Papua New Guinea (Taufa, 1974; Donovan et al., 1977). Although much is yet to be revealed about this condition, the main risk factor is the consumption of stale sago starch, a food stuff which is the staple carbohydrate for rural Papua New Guineans. It is thought that fungi that colonise the sago are responsible for the haemolytic compound that cleaves red cell membrane proteins. The condition often manifests in family clusters and a genetic predisposition has been postulated. Melanesian Ovalocytosis (MO), also known as South East Asian Ovalocytosis (SAO), is a autosomal recessive genetic disorder expressing a red cell membrane band 3 deletion in individuals who have inherited the gene responsible. The condition is subclinical but common in rural PNG where it is thought to offer some malaria protection (Bruce et al., 2000). It is reasonable to assume that as this condition is widespread in rural PNG where SHD is endemic, it may a confounding predisposing factor to the manifestation of the acute haemoltyic crisis. A number of organisms implicated in SHD have been isolated and crude haemolytic compounds were isolated as per methods of Bernheimer (Bernheimer, 1988). Red cell membrane ghosts where prepared from individuals with and without the MO band 3 deletion and exposed to the toxins. Proteins were separated using Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and the activity of the toxin was demonstrated by the cleaving of band known to be present through comparison with untreated controls. Although cleavage of bands was demonstrated by various toxin compounds no discernable difference could be identified between the two groups. This may suggest that MO is not involved as a host factor which predisposes SHD, although further studies are required to elucidate this finding