Tumour of the orbit and pterygopalatine fossa: delayed recognition of possible IgG4-related disease

Introduction
IgG4-related disease (IgG4-RD) is a systemic fibrotic-inflammatory disease characterised by elevated serum concentration of IgG4 and tissue infiltration by plasma cells. IgG4-RD is a newly recognised fibro-inflammatory condition, characterised by organ mass lesions, special histopathological appearance, and – often but not always – elevated serum IgG4 concentrations. IgG4-RD is a separate, clinically distinct disease entity, but, due to its heterogeneous manifestation, it is a subject of interest of physicians of various specialties. Histopathological examination is the gold standard in the diagnosis.

Case report
In the paper we discuss the case of a 13-year-old patient who had been diagnosed with fully symptomatic IgG4-RD nine years after initial manifestation. Although IgG4-RD is diagnosed markedly more often in adults than in children, in this case report we would like to emphasise that the disease may also occur in paediatric patients, and it constitutes both a diagnostic and therapeutic challenge in this age group.

Conclusions
IgG4-RD is a poorly recognised disease, especially in the paediatric population. To the best of our knowledge, case reports on IgG4-RD in paediatric patients available in the literature are sparse. The non-specific and heterogeneous manifestation may hinder the diagnostic process, and in some cases the disease is diagnosed accidentally, especially when it is asymptomatic. Since 2015, the first-line treatment in IgG4-RD has been glucocorticoids; however, combination therapies should not be underestimated as another method to achieve permanent remission.