[Pulmonary hypertension in chronic myeloproliferative disorders].

We report on three autopsy cases with clinical and morphological evidence of pulmonary hypertension and concurrent myeloproliferative disorders. Massive accumulations of pleomorphic, atypical megakaryocytes and thrombotic material are found within the pulmonary capillary beds. Morphometrical studies allowed us to identify on average 1,293.4 (1,145.8-1,401) megakaryocytes per one square centimetre lung tissue (standard value: 25 megakaryocytes/cm(2) lung tissue). The lungs of the controls with unaffected parenchyma show smaller numbers of megakaryocytes. It seems highly unlikely that these haematopoietic cells originate in lung capillaries in the absence of morphological correlates. Recurrent chronic microemboli consisting of megakaryocytes and thrombocytes could be held responsible for the development of secondary chronic pulmonary hypertension. Our observations suggest that pulmonary hypertension associated with chronic myeloproliferative disorders should be classified into the fourth group of the EVIAN-classification of pulmonary hypertension.