Discussion
IgG4-RD is a newly recognized condition characterized by elevated serum IgG4 and tissue infiltrates of IgG4+ plasma cells 15. IgG4-RD has been mentioned as a systemic disease since 2001 when increased serum IgG4 concentrations were reported in patients of autoimmune pancreatitis 16, but the term “IgG4-RD” was established later in 2012 to foregather some of the known conditions in patients with common characteristics 17. IgG4 is proposed to unify and be the link to individual fibro-inflammatory reactions in different organs of a patient and is found in high amounts in the serum of IgG4-RD patients 15,17.
Involvement of every organ is possible, but the nervous system is not the most commonly affected site 18, and isolated CNS involvement is rarely reported 19. Large studies of systemic IgG4-RD have shown no CNS manifestations20,21. The role of serum IgG4 levels in contributing to isolated neurological involvement is unclear 18, and biopsy-aided diagnosis, though invasive, may propose a help in this new entity of knowledge.
This report presents a 33-year-old female with the chief complaint of right eye proptosis, which developed in a period of 3 months. Our patient didn’t have any specific history except for the recurrent CVTs treated with anticoagulants. Other organs were clear of abnormalities, and upon further investigations, the diagnosis of IgG4-RD was considered. As in our case, nervous system involvement can be the only IgG4-RD presentation.
The aim of our report was to show how IgG4-RD can mimic typical symptoms of other diseases. Also, co-occurring conditions in other organ systems of the body may be present with IgG4-related neurological disease (IgG4-RND) even though the disease might need time to develop, and all of the symptoms might not be found simultaneously.
A minority of patients with IgG4-RD were reported to be younger than 50 years of age 22, and in a study of IgG4-related neurological disease, the mean age was 46 years 18. It can be a real challenge to diagnose such a condition due to its rarity and non-specific symptoms, particularly early in life, as in our case. We must recognize these patients as being at risk of other clinical issues and take appropriate measures to reduce the likelihood of a serious complication.
IgG4-RD in the nervous system most commonly manifests as hypertrophic pachymeningitis and hypophysitis (19), and we got the chance to observe diffuse pachymeningeal thickening in our case. Pachymeningitis appearing as a linear or bulging lesion along with dura matter involvement of different local areas can cause focal signs such as sensory, visual, or hearing problems and nerve palsies 23. Diffuse symptoms, for instance, headache and seizures, may be due to meningeal inflammation extending to the hemispheric and basal dura 23.
Further studies are recommended in identifying characteristics of patients with this condition because those diagnosed with acute/subacute symptoms seem to respond well to steroids 17,18. Although there is no definite treatment guideline to date, IgG4-RD response to immunosuppressive therapy and the history of immune-related conditions in the patients suggest the immune nature and inflammatory background for the pathogenesis of this disease 23. Better knowledge of the pathogenesis of IgG4-RD can guide us in defining a specific treatment.