Epidemiology of von Willebrand disease in developing countries.

There is limited information on von Willebrand disease (vWD) in developing countries. A questionnaire survey in 1998 showed that overall, less than one third of the expected number of patients with vWD in the population had been detected. Among those registered, the proportion with the severe form of the disease was relatively higher, forming up to 50% of the total, particularly in those countries with high prevalence of consanguineous marriages. Diagnosis was based on von Willebrand factor antigen (vWF:Ag) assays, vWF ristocetin cofactor (vWF:Rco) activity, and ristocetin-induced platelet aggregation (RIPA) at the reporting centers, but vWF multimer analysis was not widely available. Responsiveness to desmopressin acetate (DDAVP), which could be very significant clinically, was not often assessed. An attempt was made to assess accuracy of reporting of the prevalence of vWD by conducting a second survey aimed at normalizing the reported numbers with that of severe hemophilia A in a defined population on the presumption that the latter is less likely to be missed. These data showed that in most countries, the ratio of patients with vWD to severe hemophilia varied between 0.1 to 0.6 with a mean of approximately 0.4, as opposed to an expected ratio of approximately 1 (based on population-based data from Italy), confirming the underdiagnosis of vWD even within the same health-care system. A system for collecting more extensive and detailed data on vWD from developing countries (where 80% of the world's population lives) is required. Efforts are needed to develop national registries and make at least basic services for diagnosis and treatment widely available.