Budd-Chiari syndrome: aetiology and geography.

Sir, Mahmoud ef a/. have recently reported underlying myeloproliferative disorders (MPD) as the commonest aetiology in Budd-Chiari syndrome (BCS) in their series. There appears to be continuing controversy over the aetiological factors and their geographical variation observed in this disorder. Earlier studies from Western countries have documented polycythemia vera as the commonest aetiology, with a large number of patients in the idiopathic category.' More recently, with the use of in vitro endogenous erythroid colony (EEC) assays, as many as 80% of patients have been identified as having haemopoietic stem-cell defect with or without overt features of MPD.' Those cases, without overt features of MPD, were considered to have latent or occult MPD. However, such clonal defects in the absence of overt laboratory features of MPD have not been accepted as the aetiology by many workers, as none has been shown to progress to overt MPD, even after many years of follow-up. However, one can not overlook the haemopoietic stem-cell defect in these patients. A recent study in female BCS patients for X-inactivation by restriction-fragment-length polymorphism (RFLP), as well as EEC studies, has further strengthened the evidence for stem-cell defect as the underlying aetiology in BCS patients. Transmission electron microscopy of platelets in our BCS patients has revealed morphological changes akin to activated and exhausted platelets in the circulation, although many have shown EEC growth as well (unpublished data). A few cases of BCS have shown overt features of MPD after liver transplantation or surgery. Valla et al. and Pagliuca ef a/. in their studies have shown that patients with latent MPD in BCS when investigated showed increased red-cell mass, thereby confirming latent polycythemia vera. However, most studies have not undertaken this approach.