A diagnosis too far: chronic lymphocytic leukemia, neurosarcoidosis, motor neurone disease

<h3></h3> Sarcoid like reaction is a rare autoinflammatory disease that can affect lymph nodes and organs but does not meet the diagnostic criteria for systemic sarcoidosis. Anti-CD20 auto- antibodies have been reported to be responsible for such reactions. Although very rare, there has been associations between neurosarcoidosis and motor neurone disease (MND). We report a case presenting with sarcoid like reaction in lymph nodes following rituximab treatment for chronic lymphocytic leukaemia (CLL) and a new diagnosis of MND. A 60-year-old male patient presented with lower limb rash, left leg weakness followed by bulbar symptoms which rapidly progressed over 12-months. There was a significant history of CLL last treated with Venetoclax and Rituximab to induce haematological remission. Extensive workup demonstrated CSF pleocytosis and avid inguinal lymph adenopathy on PET. Skin and inguinal lymph node biopsies showed non-necrotising granulomas. Electomyograph met diagnostic criteria for MND. In view of the histopathological findings, the patient received a trial of steroids and infliximab for neurosarcoidosis presenting with MND. Despite treatment, the clinical course progressed like a classical MND. We discuss the diagnostic challenges of this case as to whether the patient had a causal association between the sarcoid like granulomatous disease and presentation with MND.