Two Cases of Diffuse Alveolar Haemorrhage Attributable to Human Metapneumovirus Infection: A Case Report.

Diffuse alveolar haemorrhage (DAH) is a rare but potentially life-threatening syndrome with diverse etiologies. Human metapneumovirus (hMPV) infection has rarely been reported as a cause of DAH. We report two cases of DAH associated with hMPV infection in immunocompetent adults. In both patients, bronchoalveolar lavage fluid (BALF) showed progressively haemorrhagic returns and hemosiderin-laden macrophages, consistent with DAH. Multiplex polymerase chain reaction (PCR) using BALF detected hMPV, while extensive investigations excluded autoimmune, bacterial, and other viral causes. These cases suggest that lower respiratory tract infection with hMPV can be associated with DAH, even in immunocompetent adults. Screening for hMPV should be considered in cases of DAH of unknown aetiology, and multiplex PCR using BALF is a useful diagnostic tool.