UNASSIGNED: Paraneoplastic peripheral neuropathy (PPN) caused by olfactory neuroblastoma (ONB) has not yet been reported.
UNASSIGNED: We present a rare case of an adult who hospitalized repeatedly over the past 9 months for persistent pain and numbness in the limbs. This patient was initially diagnosed with chronic inflammatory demyelinating polyneuropathy (CIDP) and treated accordingly, but neurological symptoms did not improve significantly. After this admission, FDG-PET/CT showed focal hypermetabolism of a soft-tissue mass in the nasal cavity, and further lesion biopsy suggested ONB. Combined with positive serum anti-Hu antibody, the diagnosis of PPN associated with ONB was eventually made. Furthermore, the patient\'s neurological symptoms were relieved after removal of the primary tumor, confirming the accuracy of the diagnosis.
UNASSIGNED: Our case not only expanded the clinical characteristics of ONB but also highlighted the importance of early and comprehensive tumor screening for the diagnosis of PPN.

BACKGROUND: Paraneoplastic neurological syndrome (PNS) is a rare complication in patients with cancer. PNS can affect the central, peripheral, autonomic nervous system, neuromuscular junction, or muscles and cause various neurological symptoms. Anti-Yo antibody-positive neurological paraneoplasms and anti-Hu antibody-positive neurological paraneoplasms are common, but coexistence of both types has not been described in the literature.
METHODS: Here we present a rare case of paraneoplastic neuropathy occurring in both breast and lung cancers. A 55-year-old woman was admitted to our hospital with unsteadiness while walking. The patient had a history of breast cancer two years previously. Chest computed tomography revealed a 4.6 cm × 3.6 cm mass in the right lung, which was diagnosed as small-cell lung cancer (SCLC). Blood test was positive for anti-Yo antibodies, and the cerebrospinal fluid was positive for both anti-Yo and anti-Hu antibodies, and the neurological symptoms were considered to be related to the paraneoplasm. The patient was treated with a course of intravenous immunoglobulin, without noticeable improvement. After being discharged from hospital, the patient underwent regular chemotherapy for SCLC and periodic reviews. The patient\'s neurological symptoms continued to deteriorate at the follow-up visit in April 2021.
CONCLUSIONS: This case suggests the possibility of two types of tumors appearing simultaneously with two paraneoplastic antibodies. The clinical appearance of two or more paraneoplastic tumors requires additional attention.

Paraneoplastic neurologic syndromes (PNSs) are a wide spectrum of neurologic diseases characterized by different clinical features, associated with a neoplasia, and triggered by an immune-mediated process. In most cases, it is possible to detect specific neuronal antibodies and the Hu protein is one of the most frequently recognized intracellular antigens in patients with PNSs. Small-cell lung cancer is the most common cancer associated with PNSs, followed by urological, gynecological and hematological malignancies. Otherwise, extra-pulmonary small-cell carcinomas, including Merkel cell carcinoma (MCC), have been rarely described as related to PNSs. In this article we report, for the first time in the published literature, a case of anti-Hu antibody-related subacute sensory neuronopathy in association with MCC.

Malignancies can trigger an autoimmune response against the nervous system and manifest as paraneoplastic neurological syndromes (PNS). Initial symptoms of PNS may develop up to 5 years prior to the diagnosis of the underlying malignancy. We report a rare case of PNS associated with transitional cell carcinoma of the bladder in a 70-year-old male with a 6-month history of rapidly progressive symmetric sensory neuropathy. Peripheral neuropathy serological workup was unremarkable. A paraneoplastic neuropathy panel revealed anti-Hu autoantibodies. Further evaluation with a whole-body PET scan could not identify the primary malignancy, but it showed hypermetabolic hilar lymph nodes. An endobronchial ultrasound biopsy of the hilar lymph nodes was negative for cancer. The patient developed painless hematuria 2.5 years after the onset of the sensory neuropathy. Cystoscopy with biopsy revealed non-muscle-invasive transitional cell carcinoma of the bladder. Progression of the sensory neuropathy stopped after tumor resection. This case highlights the importance of a diligent and systematic approach to diagnose PNS. A relentless search is often required to detect PNS-associated occult malignancies.

An 81-year-old woman was admitted to our hospital due to paresthesia of the extremities and difficulty in walking for three months. She underwent a total hysterectomy and bilateral salpingo-oophorectomy for large cell neuroendocrine carcinoma (LCNEC) of the endometrium seven months before the admission. The serum levels of neuron specific enolase (NSE) reduced after the surgery. She showed numbness of her limbs, disturbance of vibration, areflexia and autonomic dysfunction. Nerve conduction studies showed sensory dominant sensory neuronopathy. CT scan of her abdomen and pelvis revealed the recurrence of LCNEC of the endometrium. The serum levels of NSE was elevated and anti-Hu antibody was also positive. Other laboratory test, including autoantibodies were unremarkable. We diagnosed her as paraneoplastic sensory neuronopathy associated with postoperative recurrence of LCNEC of the endometrium. Here we show a clinical picture of anti-Hu positive paraneoplastic neurological syndrome with LCNEC of the endometrium.

The present report describes a case of anti-Hu antibody-mediated encephalopathy associated with ovarian cancer. The patient developed paraneoplastic neurologic syndromes (PNS) during the course of ovarian cancer and showed a symptom of jargon aphasia; diagnosis of PNS was made on the basis of serological and cerebrospinal examination, electroencephalogram (EEG), and magnetic resonance images. EEG initially indicated a condition of non-convulsive status epilepticus; however, levetiracetam administration facilitated complete recovery of this condition. Furthermore, immunotherapy and steroid therapy were very effective and significant improvement was achieved. PNS usually occur before the cancer is identified; however, the possibility of PNS should be considered when neurologic symptoms are noted during the course of oncologic diseases, including ovarian cancer.

A 55-year-old postmenopausal and multiparous woman presented to our department with recent memory disturbances associated with rapidly progressive positive Anti-Hu antibodies. She was subsequently diagnosed with anti-Hu antibody-related paraneoplastic limbic encephalitis. Clinical examination and imaging studies revealed a bulky cervical tumor with both parametrial and vaginal fornix extension; biopsy confirmed the tumor as cervical squamous cell carcinoma. In this case, we encountered a patient with anti-Hu-mediated paraneoplastic limbic encephalitis with a subsequent diagnosis of cervical cancer.

Prevalence of paraneoplastic encephalitis in association with recurrent neuroblastoma (NB) is rare. Here, we report a case of recurrent NB presented as paraneoplastic encephalitis, treated successfully with high dose steroids leading to complete neurological recovery. This case highlights the importance of early recognition, diagnosis, and treatment of paraneoplastic encephalitis in a pediatric patient with the new development of neurological symptoms in the background of NB. Paraneoplastic encephalitis also served as an early sign of disease relapse.