Susac Syndrome With Livedo Reticularis: Pathogenesis and Literature Review.

Susac syndrome (SuS) is a rare autoimmune endotheliopathy that affects the retina, cochlea, and central nervous system (CNS). Even fewer cases of SuS have been reported with dermatological findings, including livedo reticularis and racemosa. The case of SuS reported here presents with encephalopathy, visual disturbances, hearing loss, and a diffuse rash on the abdomen and flank. Magnetic resonance imaging (MRI) of the brain confirmed lesions within the corpus callosum, and an audiogram revealed a unilateral biphasic sensorineural hearing loss in the right ear. A skin biopsy was completed that revealed congested dermal vessels with lymphocytic perivascular infiltrates consistent with livedo reticularis and vasculopathy. Management included intravenous methylprednisolone (IVMP) and a tapering oral dose of prednisone. The patient was also administered 1000 mg of cyclophosphamide with a two-week follow-up for a repeat infusion. Cytotoxic T-lymphocytes (CTLs) and auto-endothelial cell antibodies (AECAs) are hypothesized to play a key role in the pathogenesis of SuS. Livedo reticularis occurs due to congestion of dermal vessels and can be both physiological and pathological in etiology. Pathological etiologies include autoimmune vasculopathies, connective tissue disorders, and drugs (catecholaminergic agents, amantadine, quinidine, etc.). A literature review of SuS cases with associated dermatologic findings is included. Five cases were identified, and neurologic manifestations, dermatologic manifestations, and interventions are described.