To report a case of painful, progressive tetraparesis associated with testicular seminoma and Leucine Zipper 4 (LUZP4)-immunoglobulin G (IgG) refractory to immunomodulatory treatment and orchiectomy

LUZP4-IgG is a novel antibody implicated in germ cell tumor related paraneoplastic neurological syndrome.  

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A 51-year-old male presented with a 5-week history of progressive weakness. Nerve conduction studies (NCS) and electromyography (EMG) revealed a subacute axonal polyradiculoneuropathy. MRI lumbar spine showed thickening of the cauda equina and enhancement of the lower thoracic spinal cord/conus. Cerebrospinal fluid (CSF) showed a lymphocytic pleocytosis, three oligoclonal bands, and mildly elevated protein. He was treated with intravenous immunoglobulin (IVIg) and prednisone and discharged with symptomatic improvement. Motor weakness worsened upon completion of his prednisone course. Despite restarting high-dose prednisone, he was rehospitalized two months later due to progressive neuropathy. Positron emission tomography (PET)-CT targeted retroperitoneal biopsy revealed a regressed testicular seminoma with lymph node metastasis, which was treated with orchiectomy and chemotherapy. He underwent five sessions of plasmapheresis and was discharged on prednisone. The weakness continued to progress and IVIg was trialed without success. Neurologic examination demonstrated lower-limb-predominant tetraparesis (upper limbs: proximal strength 5/5, distal 4/5; lower limbs: proximal 3/5 and distal 0/5), hypo/areflexia, and mild distal sensation loss. EMG showed severe, axonal, motor-predominant polyradiculoneuropathy. Repeat PET-CT, MRI, and CSF studies were unrevealing. Patient was tested for LUZP4 antibody in the serum and CSF, which returned positive only in serum. Oral cyclophosphamide and high-dose prednisone were initiated. At 4-month follow up, the patient had significant improvement in hand strength and had transitioned from walker to cane.

A positive serum study confirmed the diagnosis of LUZP4-IgG paraneoplastic neurological syndrome. This case highlights the importance of identifying specific serologic biomarkers, as CD8+ T-cell mediated paraneoplastic syndromes require aggressive immunotherapy.