Fibrosing mediastinitis in a child with Mendelian susceptibility to mycobacterial disease possibly due to Bacillus Calmette-Guérin

Background Mendelian susceptibility to mycobacterial disease (MSMD) is an uncommon disorder with increased susceptibility to less virulent mycobacteria including bacillus Calmette-Guérin (BCG). Fibrosing mediastinitis (FM) is also a rare condition defined by excessive fibrotic reactions in the mediastinum. So far, some infectious organisms and autoimmune diseases have been introduced as possible etiologies of FM. However, no study has ever discussed the possible association of BCG infection and FM. Case presentation In this study, we report a 3-year-old female presenting with persistent fever, weakness, and bloody diarrhea in addition to mediastinal lymphadenopathy, hepatosplenomegaly, and pleural and pericardial effusion. Further examinations established a diagnosis of MSMD based on her clinical condition, immunologic data, positive tests for mycobacterial species, positive family history, and genetic study (IL12RB1 gene, c.G1193C, p.W398S). A year and a half later, she was referred with submandibular lymphadenitis and underwent immunologic work-up which revealed high inflammatory indices, a slight reduction in numbers of CD3 + and CD4 + cells as well as elevated CD16/56 + cell count and hyperimmunoglobulinemia. Purified protein derivative (PPD), QuantiFERON, and gastric washing test were all negative. Her chest computed tomography (CT) scan revealed suspicious para-aortic soft tissue and her echocardiography was indicative of strictures in superior vena cava and pulmonary veins. She further underwent chest CT angiography which confirmed FM development. Meanwhile, she has been treated with anti-mycobacterial agents and subcutaneous IFN-[gamma]. Conclusion In summary, we described a novel case of MSMD in a child presenting with granulomatous FM possibly following BCG infection. This is the first report introducing aberrant BCG infection as the underlying cause of FM. This result could assist physicians in identifying early-onset FM in suspicious cases with MSMD. However, more studies are required to support this matter. Keywords: Mendelian susceptibility to mycobacterial disease, MSMD, Fibrosing mediastinitis, FM, Bacillus Calmette-Guérin, BCG