Granuloma in the explanted lungs: Infectious causes and impact on post-lung transplant mycobacterial infection

The significance of granuloma in explanted lungs of lung transplant recipients (LTR) on the development of post-transplant mycobacterial infection is unclear.

A retrospective review comparing LTRs and heart-lung transplant (H-LTR) recipients with granuloma in the explanted lungs between 2000 and 2012 (excluding those LTRs with granuloma due to sarcoidosis) and LTRs or H-LTRs without granuloma. Patients were followed for 2 years post-transplant.

A total of 144 LTRs and 4 H-LTRs with granulomas (75 necrotizing and 73 non-necrotizing) and a comparator cohort of 144 LTRs and 4 H-LTRs without granuloma were analyzed. In LTRs with granulomas, identification of infectious organisms was more common by histopathology (35 AFB and 22 fungal) compared to cultures (six NTM and seven fungal) taken around time of the transplant. LTRs with granulomas were more likely to have pre-transplant non-tuberculous mycobacteria (NTM) infection compared to LTRs without granuloma; P < .01. In the multivariate analysis, having granuloma or positive mycobacterial cultures at time of transplant were associated with increased risk of post-transplant mycobacterial infection (HR = 1.8 95% CI [1.024-3.154]; P = .041 and HR = 2.083 95% CI [1.011-4.292]; P = .047). Although there was a trend toward increase mycobacterial disease in those with granulomas P = .056, there was no difference in survival post-transplantation between those with or without granuloma in the explanted lung; P = .886.

The presence of granuloma in the explanted lungs of LTRs or positive mycobacterial cultures at time of transplant is associated with an increased risk of mycobacterial infection post-transplant.