Intrathecal rituximab for IgG4-related hypertrophic pachymeningitis

Intrathecal administration of rituximab—an anti-CD20 monoclonal antibody—is emerging as a promising therapeutic strategy for B cell lymphomas of the central nervous system (CNS).1 2 The rationale for administering rituximab directly into the cerebrospinal fluid (CSF) stems from the need to achieve optimal therapeutic concentrations within the intrathecal compartment. Rituximab, in fact, has a high molecular weight and only 0.1%–0.5% of its plasmatic concentrations crosses the ‘blood-brain barrier’ (BBB) after intravenous infusion.1 In addition, despite inducing prolonged depletion of circulating B lymphocytes, systemic rituximab does not affect malignant B cells in CNS lymphomas.2 Hypertrophic pachymeningitis (HP) is the most frequently encountered CNS manifestation of IgG4-related disease (IgG4-RD), a fibroinflammatory condition of unclear aetiology.3 The intrathecal synthesis of IgG4 in patients with IgG4-related hypertrophic pachymeningitis(RHP) and the clinical improvement after rituximab in patients with systemic involvement, support a pathogenic role of B lymphocytes.4–6 Among IgG4-RD manifestations, however, IgG4-RHP stands out for a certain resistance to intravenous rituximab raising the possibility that systemic administration might not be as effective on putative pathogenic B cells residing in inflammatory niches within the CNS.4 Here, we report the first case of IgG4-RHP treated with intrathecal rituximab. A young adult patient was admitted in April 2015 for rapidly progressive frontal headache and complete visual loss on the right eye. Imaging studies of the head and neck revealed diffuse pachymeningitis with bone erosions, thickening of the nasal septum, hard palate tumefaction, and bilateral optic neuritis; neuro-ophthalmological examination reported asymmetrical signs of optic nerve fibre atrophy (right >left) with loss of colour vision and complete depression of the visual field on the right eye (figure 1 and see online supplementary figure e1). Laboratory and CSF analyses at the time of admission are reported in online …