A 77-year-old man with a history of left nephrectomy for renal cell carcinoma and partial hepatectomy for cholangiocarcinoma underwent 18F-FDG PET/CT for assessment of an irregular lung lesion. FDG-PET demonstrated development of an intensely avid spiculated left lower lobe pulmonary lesion and intensely avid left pulmonary hilar nodes, raising suspicion for a malignancy. Eleven days following the PET study, the patient was admitted to hospital with an altered mental state. CT brain revealed diffuse round hyperdensities within the brain parenchyma. Microbiology of the lung lesion was positive for Nocardia Beijingensis and he was subsequently diagnosed with disseminated nocardiosis.

BACKGROUND: Anti-interferon-gamma autoantibody-associated immunodeficiency syndrome is a rare and underrecognized adult onset immunodeficiency syndrome associated with severe opportunistic infections such as disseminated nontuberculous mycobacterium. Few cases have documented a relationship with IgG4-related disease. Concomitant diagnoses of these diseases present a diagnostic and management challenge.
METHODS: A 61 year old man of Southeast Asian descent with pulmonary mycobacterium avium complex infection presented to our hospital system with a new skin rash and worsening lymphadenopathy. He was eventually diagnosed with IgG4-related disease through excisional nodal biopsy. He was managed with immunosuppressive treatment with prednisone, rituximab and cyclophosphamide. He later re-presented with disseminated mycobacterium avium complex infiltration of his joints, bones and prostate. Original titers of anti-interferon-gamma autoantibodies were falsely negative due to being on immunosuppressive therapy for his IgG4-related disease. However, anti-interferon-gamma autoantibody titers were re-sent after immunosuppression was held and returned strongly positive.
CONCLUSIONS: This case reviews diagnostic criteria and discusses management strategies with existing challenges in treating a patient with concomitant adult onset immunodeficiency syndrome, IgG4-related disease and a disseminated mycobacterial avium complex infection.

Patients with anti-interferon (IFN)-γ autoantibodies have weakened immune defenses against intracellular pathogens. Because of its low incidence and non-specific symptoms, diagnosis of anti-IFN-γ autoantibody syndrome is difficult to establish during the early stages of infection. Here, we report a patient with high titers of serum anti-IFN-γ autoantibodies suffering from opportunistic infections. The patient presented with intermittent fever for 2 weeks. During his first hospitalization, he was diagnosed with Talaromyces marneffei pulmonary infection and successfully treated with antifungal therapy. However, multiple cervical lymph nodes subsequently became progressively enlarged. Mycobacterium abscessus infection was confirmed by positive cervical lymph node tissue cultures. High-titer serum anti-IFN-γ antibodies were also detected. Following anti-M. abscessus therapy, both his symptoms and lymph node lymphadenitis gradually improved. Anti-IFN-γ autoantibody syndrome should be considered in adult patients with severe opportunistic coinfections in the absence of other known risk factors.