ＩｇＧ４関連疾患

PURPOSE: Hepatic actinomycosis is a rare granulomatous disease caused by an opportunistic Gram-positive bacillus of the genus Actinomyces. We report an unusual association between hepatic actinomycosis and IgG-4 related disease. CASE DESCRIPTION: A 70-year-old man was admitted to the University Hospital of Reunion Island for asthenia and abdominal pain. Laboratory tests showed hepatic cholestasis and inflammatory reaction without cytolysis. The computer tomography scanner (CT scan) revealed a large hepatic mass in segment IV. IgG4 related disease (IgG4-RD) was diagnosed following liver biopsy. Despite the use of corticosteroids, the lesions progressed. A new biopsy was performed and a PCR test returned positive for Actinomyces spp. We observed patient improvement after 4 months of treatment with amoxicillin and discontinuation of corticosteroids. CONCLUSIONS: Clinical presentation, imaging characteristics, and diagnostic challenges are strikingly similar between hepatic actinomycosis and IgG4-related disease. However, distinguishing between these two disorders is essential - as the treatment of one may worsen the course of the other. Knowing and understanding the interactions between these two disorders can only be achieved through an integrated and collaborative approach involving various disciplines.

Kimura disease typically presents with painless head and neck swelling in young adults of Asian descent, accompanied by peripheral eosinophilia and elevated serum IgE. We report a case of Kimura disease in a woman in her early 30s presenting with a slowly enlarging epitrochlear mass, diffuse encasement of the median and medial brachial cutaneous nerves, and a concurrent prurigo nodularis-like papular rash affecting all 4 extremities. The diagnosis required over 1 year of investigation and 5 tissue specimens, including 2 nondiagnostic core-needle biopsies, before near total excision was performed. The excision revealed characteristic histopathologic features, including hyperplastic reactive secondary lymphoid follicles with preserved architecture, a marked eosinophilic infiltrate with eosinophilic microabscesses, postcapillary venule proliferation, and patternless stromal fibrosis. Immunohistochemistry demonstrated a raised IgG4:IgG plasma cell ratio of approximately 1:1, with 150-200 IgG4-positive plasma cells per high-power field, raising the differential of IgG4-related disease; however, the absence of storiform fibrosis and obliterative phlebitis, combined with the clinical and serologic profile, favored Kimura disease. This case is notable for its rare epitrochlear location, extensive neural involvement, concurrent diffuse cutaneous eruption, and histopathologic overlap with IgG4-related disease, highlighting the diagnostic challenges posed by atypical presentations of Kimura disease.

Helminth-related immune responses may intersect with autoimmune rheumatic diseases, but disease-specific patterns remain incompletely understood. This study aimed to investigate anti-Toxocara canis seroreactivity and its immunological and clinical correlates in rheumatoid arthritis, systemic lupus erythematosus, and spondyloarthritis. In this cross-sectional case-control study, 442 individuals were evaluated across disease-specific comparisons. Serology followed a sequential strategy using native T. canis excretory-secretory antigen for initial IgG screening and a recombinant chimeric antigen for confirmatory IgG, IgG1, and IgG4 assessment. Cytokines, eosinophil counts, socioeconomic variables, disease activity, and functional disability were analyzed using adjusted regression models. Total anti-T. canis IgG seroreactivity was frequent across groups. Higher adjusted point estimates were observed in rheumatoid arthritis, systemic lupus erythematosus, and spondyloarthritis. SLE was the only disease group showing a nominally significant association with IgG seroreactivity compared with its respective control group (OR 2.44, 95% CI 1.16-5.14), although no serological association remained significant after FDR correction. SLE also showed a nominal signal of lower IgG4 seroreactivity than controls in the standard adjusted model (OR 0.20, 95% CI 0.04-0.99), but this finding did not remain significant after FDR correction or in small-cell sensitivity analyses. Higher eosinophil counts were associated with lower SLEDAI scores in negative binomial models (IRR per 100 eosinophils/mm³: 0.56, 95% CI 0.36-0.86), and this association persisted after adjustment for medication use, although it should be interpreted as exploratory given the low SLEDAI distribution and limited number of active disease events. Anti-T. canis seroreactivity was frequent across autoimmune rheumatic diseases and showed disease-specific exploratory patterns. In SLE, higher total IgG seroreactivity coexisted with a cautious, hypothesis-generating IgG4 signal, while eosinophil counts showed an exploratory independent association with lower SLEDAI scores. These findings suggest that helminth-related immune signatures may vary across autoimmune disease contexts and should be interpreted as exploratory associations rather than evidence of active infection or causal immunomodulation.

A rare case of a 26-year-old male presenting with abdominal pain and jaundice was initially suspected to be a gallbladder malignancy based on imaging findings of a gallbladder fossa mass and biliary strictures. Serial imaging, including ultrasound, CT, PET-CT, and endoscopic retrograde cholangiopancreatography (ERCP), revealed a hypermetabolic mass with biliary obstruction but no gallstones. Elevated serum IgG4 levels and a marked clinical response to steroids led to the diagnosis of IgG4-related sclerosing cholangitis (IgG4-SC) and cholecystitis, an uncommon presentation that often mimics malignancy or acute cholecystitis. This case highlights the diagnostic challenges and importance of considering IgG4-related disease (IgG4-RD) in young patients with inflammatory biliary masses and emphasizes multidisciplinary management to avoid unnecessary surgery.