Telomere biology disorder presented with de novo pneumocystis jirovecii pneumonia: A case report.

Introduction: and Importance: Telomere biology disorder (TBD), which is a genetic disorder marked by mutations in telomere-maintenance genes, leading to shortened telomere, accelerated aging, and multi-systems effects including the pulmonary and immune systems. Opportunistic infections, such as Pneumocystis jirovecii pneumonia (PJP), occurring de novo are rare in TBD, presenting unique diagnostic and therapeutic challenges. Case presentation: We present a female in her seventies with chronic dry cough and exertional dyspnea referred for evaluation of interstitial lung disease (ILD). Bronchoalveolar lavage confirmed PJP despite no established immunosuppression. High-resolution chest CT revealed progressive infiltrates and fibrotic lung disease. Surgical lung biopsy showed organizing pneumonia, diffuse alveolar damage, and fibrosis, consistent with probable usual interstitial pneumonitis (UIP). Telomere studies confirmed TBD, with her lymphocyte and granulocyte telomere lengths between the 1st and 10th percentiles. Clinical discussion: This case illustrates a rare presentation of PJP de novo in a patient with TBD, highlighting opportunistic infections risk in those patients without immunosuppression and before transplantation. Management requires a multidisciplinary approach with early genetic testing, antifibrotic therapies, and prophylactic treatments to prevent infections. Conclusion: We report a rare case of de novo PJP pneumonia in a patient with TBD is unreported in the literature. High clinical suspicion, quantitative CD4 evaluation, and consideration of PJP prophylaxis prevent an otherwise fatal outcome.