Familial myeloproliferative disease

The occurrence of one or more myeloproliferative disease (MPD) syndromes in 42 families is described. MPD appeared in a single generation in 10 families, two generations in 30 families and three generations in two families. In contrast to sparse case reports of familial polycythaemia vera, familial essential thrombocythaemia, or familial agnogenic myeloid metaplasia, in which all the involved members presented with the same MPD, 21 of the 42 families in the present series had members who presented with different MPD variants. The occurrence of multiple disease phenotypes in 'MPD families' is entirely consistent with the accepted theory of MPD as a disease arising from clonal expansion of a pluripotential haematopoietic precursor cell (PHPC) that retains its pluripotentiality and produces an array of inter-related syndromes, each named for the predominant haematic cell type involved in the proliferation. Changes in disease phenotype during the course of MPD and 'hybrid' phenotypes at the time of diagnosis are common. This report challenges the previously accepted belief that PV and other MPD variants are sporadic and randomly-occurring, and that familial occurrence of MPD is rare. The ability to identify 'MPD families' by surveying a large population of patients with MPD through the Internet, as was done in this study, and heightened awareness of familial occurrence and its phenotypic heterogeneity, should facilitate further characterization of the mode of inheritance in familial MPD and the nature of the gene mutations responsible for the dysregulation of haematopoiesis.