Fatal Human Metapneumovirus Infection in Stem Cell Transplant Recipients.

The importance of human metapneumovirus (hMPV), a recently discovered human respiratory virus, in hematopoietic cell transplant (HCT) recipients is not known. We retrospectively surveyed 211 bronchoalveolar lavage samples (BAL) from symptomatic adults with new or changing pulmonary infiltrates after HCT during five-year period using a quantitative real time RT-PCR assay. Medical records, radiographic studies, biopsy specimens, and autopsy material were reviewed. hMPV was detected in 8/211 (3.8%) BAL specimens from 5/162 (3%) patients. The median titer of hMPV was 9.0 x 10⁶ copies/ml of BAL fluid (range 5.5 x 10⁴ to 3.5 x 10⁸). Persistent hMPV infection was noted in all 3 patients who had multiple samples tested. hMPV was also detected in lung tissue in 1 of 2 samples tested. Infected patients were between the ages of 24–54 years, and became symptomatic within the first 40 days post transplant. Initial symptoms included fever, cough, nasal congestion, and sore throat. Clinical findings near the time of diagnosis included respiratory failure, pulmonary hemorrhage, and culture-negative septic shock. Four patients died as a result of acute respiratory distress and pulmonary disease with clinical and autopsy diagnoses of “idiopathic pneumonia.” We conclude that hMPV infection is associated with respiratory failure in immunocompromised adults and may result in fulminant respiratory decompensation in the post transplant period. Prospective studies of the role of this virus in idiopathic pneumonia syndromes of immunocompromised patients are warranted.