Selective IgM Deficiency Presenting As Cryptogenic Organizing Pneumonia

Selective IgM deficiency is a rare disorder that may present with severe and recurrent infections. It is associated with atopic, autoimmune, hematologic, and malignant disorders; however interstitial lung disease is rare. We present a patient with selective IgM deficiency identified after diagnosis of cryptogenic organizing pneumonia. Clinical exams, imaging, biopsy, and immunologic laboratory evaluation. 35 year old female with history of Hashimoto’s thyroiditis presented initially to pulmonology for evaluation of progressive dyspnea and cough for 1 year. She was found to have reticulonodular opacities and bronchiectasis on high definition CT scan, and was diagnosed with cryptogenic organizing pneumonia after bronchoscopy and open lung biopsy. She was referred to allergy/immunology to evaluate a possible allergic component to her cough with positive skin prick testing to dust mite. Upon further questioning, she endorsed multiple sinus infections prompting an immune deficiency evaluation. Labs revealed decreased total IgM level of 27 mg/dL with normal IgA and IgG. Flow cytometry demonstrated low normal CD4+ cells, normal CD8+ and NK cells. Isohemagglutinins were present, and antigen-specific IgG antibody responses to tetanus and pneumococcal antigens were normal. Secondary hypogammaglobulinemia was excluded. Despite treatment, the patient continues to have cough but no new infections. Selective IgM deficiency is a rare disorder that should be considered in the work up of recurrent infections and bronchiectasis. Interstitial lung disease in patients with hypogammaglobulinemia has been described. An immune deficiency workup should be considered in patients presenting with interstitial lung disease, especially with associated autoimmune and atopic disease.