Objective:

To describe a case of IgG4-related hypertrophic pachymeningitis (IgG4-RHP) as a differential diagnosis of Neuromyelitis Optica (NMO).

Background:

IgG4-RHP is a rare fibroinflammatory condition characterized by dura mater thickening associated with IgG4-related disease (IgG4-RD). The typical presentation includes headache, cranial nerve palsy, and visual disturbances due to the compression of neurovascular structures. Most patients present elevated plasma and cerebrospinal fluid (CSF) levels of IgG4. The gold standard for diagnosis is histopathology, which may show lymphoplasmacytic infiltration of IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis.

Design/Methods:

Not applicable.

Results:

A 31-year-old female patient with controlled hypertension presented with blurred vision in the left eye, which had been progressively worsening for 1 year, accompanied by pulsatile headache in the left temporal region. She sought emergency care due to an acute episode of pain and blindness in the left eye, without deficits in the right. On physical examination, there was an absent direct photomotor reflex on the left and an absent indirect response on the right, with mild proptosis on the left. She was unable to count fingers on left eye field testing and could only perceive light. There was partial paresis of the left inferior oblique muscle. Orbital MRI showed asymmetric hyperintensity of the left optic nerve, suggesting NMO on the left. Normal levels of IgG4 were found in both serum and CSF, along with negative results for oligoclonal bands and anti-aquaporin 4 antibodies. Due to persistent symptoms, further investigation included a neurosurgical biopsy of the pachymeninges, which revealed IgG4-mediated disease through immunohistochemistry.

Conclusions:

 IgG4-RHP shares clinical and pathological features with other forms of hypertrophic pachymeningitis. The typical presentation of NMO may be confused with IgG4-RHP, even in the presence of normal serum and CSF IgG4 levels. Therefore, meningeal sample analysis is crucial for confirming the diagnosis.