Lung biopsy isolated Pneumocystis jirovecii as well as CMV, however the changes seen were more in keeping with PCP than viral pneumonitis.
Histology
The wedge biopsies show acute lung injury. There is a mixture of organizing alveolar exudates, with more acute cellular/fibrinous exudates, including some hyaline membrane elaboration. The alveolar walls are mildly thickened with prominent type II pneumocytes.
Within the fibrinous exudates, a number of diagnostic clusters of pneumocystis organisms are identified on silver staining. In addition, rare cells show a dark burgundy-red inter-nuclear inclusion, consistent with cytomegalovirus. This is also confirmed by CMV immunohistochemistry. The immunohistochemistry for herpes simplex virus is negative.
The inflammatory pattern is probably best considered a type of organizing diffuse alveolar damage. The typical haemorrhagic, necrotising pneumonitis of CMV / HSV viral disease is not identified here, therefore, I suspect that the lung injury in this case is mostly due to pneumocystis.