Background/Purpose: Susac Syndrome is a rare autoimmune condition causing microvascular occlusions in the brain, retina and inner ear leading to the characteristic triad of encephalopathy, branch retinal artery occlusion (BRAO), and sensorineural hearing loss, potentially leading to permanent disability and death if untreated. Approximately 400 cases of Susac Syndrome have been reported since its initial description in the 1970s. Only a handful of cases of Rituximab use in Susac Syndrome have been reported in the literature. The goal of this descriptive study is to highlight our experience with Rituximab from one of the largest cohorts of Susac Syndrome in the world.

Methods: A retrospective chart review of sixty-eight patient meeting the European Susac Consortium criteria was performed identifying all patients treated with Rituximab. The following were recorded: patient demographics, presenting signs/symptoms, whether the full triad of encephalopathy, vision and hearing loss were present, as well as immunosuppressive medications initiated, length of follow up and whether a patient had a flare while on immunosuppression. Rituximab initiation was divided into induction and rescue therapy. Rituximab was considered an induction therapy if it was given when Susac Syndrome was first diagnosed and rescue therapy if it was used after a patient flared while on another immunosuppressive agent. Flares were defined by objective changes in brain MRI, fluorescein angiography or audiometry in addition to clinical symptoms. Flares were considered to have occurred during maintenance therapy if the flare occurred after three months from the first infusion of Rituximab.

Results: Rituximab was used as either induction or rescue therapy in forty patients (58%) within the Susac Syndrome cohort. Twenty-nine patients (72%) receiving Rituximab had the full triad of Susac present at the time of diagnosis. Twenty-eight patients (70%) on Rituximab were followed at least twelve months. Rituximab was utilized either as monotherapy or in combination with other therapeutics such as IVIG or Mycophenolate Mofetil (MMF). Rituximab was used for induction therapy in nineteen patients and rescue therapy in twenty patients. Three patients out of forty flared (7%) while on Rituximab, all were on maintenance therapy at the time of the flare (3/29 flared when isolating to only those patients followed for at least a year (11%)). Flares were a mix of ocular (2) and brain (1). One patient flared while on Rituximab as monotherapy, another was on a combination with MMF 1,000 mg and another on IVIG. The average length of follow up was 3.5 years.

Conclusion: This is the largest cohort of patients with Susac Syndrome treated with Rituximab. The majority of patients did well with only three (7%) flaring while on Rituximab. In the literature, the triad of Susac Syndrome is present in less than twenty percent of patients. In our cohort of patients on Rituximab, the triad was present in seventy-two percent of patients at diagnosis indicating more serious disease. Rituximab has been utilized for multiple decades and considered a well-tolerated therapy, it’s use in the treatment for Susac Syndrome should be further explored.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rituximab-in-the-treatment-of-susac-syndrome-single-center-descriptive-study-with-a-large-susac-cohort/