This work is the largest study of relationship between Pulmonary hypertension and myeloproliferative neoplasms and the first to study the correlation between JAK-2 allele burden and pulmonary hypertension. Through this work we made a quick review of myeloproliferative neoplasms and pulmonary hypertension and Jak-2 allele mutation and then demonstrate the results of our study. No correlation between JAK-2 allele burden and Pulmonary hypertension which was prevalent in 12% of studied cases.