Multiple Myeloma (MM) is a series of hematological malignant disease, in which there is abnormal proliferation of neoplastic plasma cells that secrete large amounts of monoclonal immunoglobulin (M protein), resulting in extensive bone destruction, and repeated infection, anemia, hypercalcemia, hyper viscous syndrome and renal insufficiency. There is high incidence in the middle-aged and elderly people. The overall incidence of MM is 1.5-2/100000, ranking second in hematological malignancies.

Pulmonary hypertension (PH) is defined by a mean pulmonary artery pressure ≥ 25 mmHg at rest measured during right heart catheterization¹. Pulmonary Arterial Hypertension (PAH) is the first one of five categories of PH¹, which is hemodynamically characterized by pre-capillary pulmonary hypertension (pre-capillary PH). It is defined by pulmonary arterial wedge pressure (PAWP) ≤ 15 mmHg and pulmonary vascular resistance (PVR) >3 Wood units, resulting from causes other than other diseases (including chronic respiratory diseases, chronic thromboembolic diseases and other rare diseases) that may result in pre-capillary PH².