HSV-pneumonitis in a patient with lung cancer receiving check point inhibitors - a case report.

Background: Herpes simplex virus (HSV) is commonly associated with oro-facial and genital manifestations. It rarely causes encephalitis and even less commonly, in heavily immunosuppressed patients, visceral disease or bronchopneumonitis. We present a case of cytologically-proven, PCR-positive HSV-1 tracheobronchitis and pneumonitis in a patient with less severe immunocompromise.

Case presentation: A 64 year old white man with steroid-induced diabetes mellitus and progressive small-cell bronchial carcinoma despite chemo- and immunotherapy with two checkpoint inhibitors presented with symptoms of lower respiratory tract infection. Community-acquired pneumonia was suspected and empirical broad-spectrum antibacterial treatment was initiated. Chest CT-scan revealed ground-glass opacities and tree-in bud lesions. Cytology of BAL showed extensive cytopathic effects typically caused by infection with herpes virus and PCR confirmation of HSV-1. Acute phase HSV serology was positive for IgG and borderline for IgM. The patient deteriorated clinically due to tumor progress and infection despite high-dose acyclovir therapy and died 2 weeks after admission.

Conclusions: We report an unusual case of fatal HSV-1 pneumonitis due to reactivation in a patient with lung cancer, steroid-induced diabetes and treatment with two checkpoint inhibitors. In immunosuppressed patients with non-improving pneumonia invasive diagnostic procedures are warranted including cytology and molecular diagnostics.