Pneumonitis post-haematopoeitic stem cell transplant - cytopathology clinches diagnosis.

Background: Primary BK virus (BKV) infection is probably acquired by the respiratory route in childhood, and latent virus persists principally in the urinary tract. BKV reactivation is implicated in late onset haemorrhagic cystitis (HC) post Haematopoietic Stem Cell Transplant (HSCT). There is emerging evidence that BKV can cause life-threatening pneumonitis in immunocompromised individuals.

Objectives: To describe the first known case of BKV pneumonitis in an adult HSCT recipient.

Study Design/results: A 19-year old male underwent an ABO-incompatible, volunteer unrelated donor allogeneic HSCT for high risk AML. The post-transplant period was complicated by moderate-severe cutaneous and gut acute graft-versus-host disease (aGVHD) and severe HC, attributable to BKV. Treatment encompassed intensification of immunosupression for aGVHD and weekly intravenous (IV) cidofovir (2.5mg/Kg) for BK viruria. He was readmitted with presumed septic shock and acute renal failure. After a transient improvement on broad spectrum antibacterials, he suffered significant respiratory deterioration. CT imaging revealed diffuse 'ground-glass' attenuation. Cytopathological assessment of a broncho-alveolar sample (BAL) was consistent with polyomavirus pneumonitis. No other cause was found to account for the respiratory deterioration. He did not respond to therapy and died of multi-organ failure.

Conclusions: BKV is implicated in haemorrhagic cystitis in HSCT recipients but not routinely considered as a cause of pneumonitis. There are just 5 other cases in the literature, including 3 patients with AIDS. BKV should be considered as a possible cause of pneumonitis in HSCT recipients.