A Potentially Fatal Complication of Immunosuppression: Disseminated Nocardiosis

Introduction: IgG4-related disease is an immune-mediated condition that can affect nearly every organ system and diagnosis is established through biopsy of involved tissue, demonstrating lymphoplasmacytic infiltration rich in IgG4-positive plasma cells and lymphocytes. Kidney manifestations include tubulointerstitial nephritis and IgG4-related membranous nephropathy. We present a rare case of disseminated nocardiosis in a patient treated with glucocorticoids and Rituximab for IgG4-related kidney disease. Case Description: A 68-year-old man initially presented to our clinic in 2019 and after an extensive work up was diagnosed with IgG4-related membranous nephropathy. He achieved remission with a course of glucocorticoids before developing recurrence of his disease four years later for which he was treated with prednisone and rituximab. He presented the emergency department several weeks later with progressive generalized weakness, dyspnea, and multiple cutaneous nodules on his scalp, posterior calves, and upper back. A chest CT demonstrated a 4.5 cm cavitating lesion. Biopsy of a cutaneous lesion confirmed nocardiosis. He was initiated on antimicrobial therapy in collaboration with infectious disease specialists. The patient subsequently developed neurologic symptoms and underwent brain imaging with an MRI that demonstrated extensive enhancing lesions consistent with septic emboli and an intraparenchymal abscess. Unfortunately, his disease continued to progress despite medical therapies. In accordance with the patient’s wishes, care was transitioned to a comfort-based approach. Discussion: This case highlights an underrecognized complication in patients with IgG4-related disease receiving immunosuppressive therapy. Nocardia is an opportunistic pathogen that primarily affects immunocompromised individuals and can present with pulmonary, central nervous system, or cutaneous involvement and carries a high mortality rate. Glucocorticoids are the cornerstone of therapy for IgG4-related disease and suppression of cell-mediated immunity increases susceptibility to opportunistic infections such as nocardiosis. Given the potentially severe consequences of disseminated nocardiosis, clinicians should maintain a high index of suspicion in immunosuppressed patients presenting with nonspecific symptoms as early recognition and appropriate antimicrobial therapy are essential to improving outcomes.