In response to Neck abscess: An unusual clinical presentation of immunoglobulin G4-related disease.

We thank Dr. Ghogomu for his comments and interest in our recent article. The author of the Letter to the Editor reports a case that is partly similar to ours in terms of clinical presentation but with a final diagnosis of tularemia. The case described by Dr. Ghogomu et al. showed severe sore throat, chills, fever, and night sweats besides neck swelling, and thus initially was presumed a viral or bacterial pharyngitis. Our patient was referred to us with a 2-week history of asymptomatic bilateral neck mass. In our specific case, the hypothesis of tularemia was quite unlikely because the patient had none of the common risk factors for infection: insect bites, contact with animals, hunting, eating undercooked wild animal meat, and drinking spring water. The patient lived in an urban area. Furthermore, tularemia usually starts abruptly, with the onset of fever, chills, headache, and other flu-like symptoms even in the glandular form. In the case described by Dr. Ghogomu et al., the histological evaluation showed necrotizing granulomatous inflammation. In our case, there was granulomatous tissue but also pronounced fibrosis, lymphoplasmacitic infiltration, and expansion of the interfollicular zone, which are typical of IgG4-related diseases. The immunological response to tularemia is another unclear fact in literature. Some authors argue that IgG2 antibodies are the predominant IgG subclass against tularemia, whereas IgG4 antibodies are below the detection level in serum samples. In our case, immunohistochemical study of the specimen revealed positivity for IgG4. There are no reports in literature of a secondary IgG4 response to tularemia lymphadenitis. However, we agree with the author that our understanding of IgG4-related disease is limited and still evolving, so all differential diagnoses should be kept in mind and examined.