Primary immunodeficiencies (PID) represent a heterogeneous group of more than 400 inherited conditions with associated immune dysfunctions. Though severe recurrent/chronic infections are the main cause of mortality and morbidity in PID, immune dysregulation manifesting with oncological and autoimmune or autoinflammatory conditions involving various organs and systems have been the focus of research in the recent years.~The interstitial lymphocytic lung disease (ILLD) is one of the recently characterized non-malignant PID complications. Immune dysregulation in ILLD causes reactive bronchi-associated lymphoid tissue (BALT) hyperplasia that manifests in several pathomorphological forms: follicular bronchiolitis (FB), nodular lymphoid hyperplasia (NLH), and lymphocytic interstitial pneumonia (LIP). Treatment of ILLD patients with various immunosuppressive drugs leads to inconsistent results ranging from partial\transient effect to no effect at all and has been often associated with adverse effects and an increase in infections' rate. Therefore there is a need for targeted therapy of ILLD. In small cohorts of adult PID patients rituximab in combination with azathioprine proved to be effective. Yet, the reports are scarce and there is currently no consensus on ILLD treatment, especially in children.~The study will collect and analyze information on the effectiveness and safety of ILLD monotherapy with rituximab or abatacept, chosen predominantly based on the pathomorphological characteristics of lymphoid infiltration, as well as genetic defects, in a cohort of pediatric patients with PID.
The rationale for this retrospective study is to evaluate the efficacy and safety of abatacept and rituximab treatment of ILLD in a cohort of pediatric patients with different forms of PID, who received one of the two therapy regimens predominantly based on the lesions histopathology.