Dermatopathic Lymphadenopathy with Talaromyces marneffei Infection Mediated by Anti-Interferon γ Autoantibodies: A Case Report with a Literature Review

Background: Dermatopathic lymphadenitis (DL) is a rare reactive lymphoproliferative disorder often secondary to chronic dermatological conditions, which can be clinically misdiagnosed as lymphoma and other malignant diseases. Anti-IFN-γ autoantibodies can predispose adults to rare opportunistic infections, but reports of DL combined with Talaromyces marneffei (TM) infection are limited. Case Description: A 56-year-old male patient presented with recurrent rashes, significant itching, desquamation, and multiple lymph node enlargements, accompanied by fever, night sweats, and weight loss. Lymph node biopsy revealed dermatopathic changes and reactive lymphoid hyperplasia. TCR and IGH gene rearrangements demonstrated negative results, and no abnormal phenotypes were detected by peripheral blood flow cytometry. Hematological and immunological tests revealed elevated white blood cells, neutrophils, and IgE levels, along with positive anti-IFN-γ autoantibodies (29.22 ng/mL). NGS testing of secretions from the ulcerated skin area of the parotid gland confirmed TM infection. The diagnosis was determined as anti-IFN-γ autoantibody-mediated TM infection, complicated by DL and reactive lymphoid hyperplasia. Antifungal therapy with amphotericin B combined with voriconazole was administered, along with symptomatic and immunomodulatory treatments. Lymph node enlargement and systemic symptoms significantly improved, and the rash completely resolved. Conclusion: This case suggests that in adult patients with diffuse skin lesions and systemic inflammatory reactions, if accompanied by multiple lymph node enlargements and pathological findings of cutaneous lymphadenitis, potential immune deficiencies related to anti-IFN-γ autoantibodies should be considered. For adults with unexplained lymphadenopathy accompanied by fungal infection, testing for anti–interferon-γ autoantibodies is recommended to identify potential underlying immune abnormalities and to inform subsequent individualized immunological assessment and therapeutic decision-making. Keywords: dermatopathic lymphadenopathy, Talaromyces marneffei , anti-interferon gamma autoantibody, pathologic diagnosis