(705) Connective Tissue Malignancies and Paraneoplastic Syndromes: What Are We Missing?

Introduction: Anti-Hu antibodies are the most frequent in paraneoplastic neurological syndromes, most associated with small cell lung cancer. The pleomorphic clinical presentation of anti-Hu PNS, ranging from peripheral nervous system (eg, sensory neuropathy, gastroparesis) to CNS (eg, limbic encephalitis, cerebellar ataxia) involvement, poses a diagnostic challenge. We describe a case of progressive weakness and ballistic movements found to have a thigh rhabdomyosarcoma associated with Anti-Hu antibodies.

Description: A 49-year-old male presented to the ED with progressive generalized weakness, unstable gait, dysphagia, 60lb weight loss, and abnormal upper extremity movements over several months. Initial neurologic work-up was unrevealing. After discharge, the patient’s condition progressed with inability to ambulate, dysphagia, and fatigue. Upon return to the hospital, a physical exam revealed a palpable mass in the left inner thigh. Imaging and pathology confirmed high-grade rhabdomyosarcoma with regional metastasis. As part of the paraneoplastic syndrome work-up, Anti-Hu Abs were detected with a brainstem syndrome and ganglionopathy with ballistic movements. High-dose steroids, PLEX, and IVIG were initiated with poor response, and Imuran was recommended. The patient’s core symptoms have improved and become manageable.

Discussion: Early identification of paraneoplastic syndrome is crucial due to its significant impact on patient outcomes. Paraneoplastic neurological syndromes (PNS) often precede cancer diagnosis. Prompt recognition and treatment can alleviate neurological symptoms and lead to the discovery of the associated malignancy. In this case, early detection of the paraneoplastic syndrome led to identifying a hidden rhabdomyosarcoma, emphasizing timely diagnosis. A physical examination remains essential in diagnosing complex conditions like PNS. While imaging is valuable, subtle clinical findings can be pivotal. In this case, a palpable mass in the thigh during a detailed exam led to the rhabdomyosarcoma diagnosis. Early suspicion of paraneoplastic syndromes in patients with nonspecific neurological symptoms is vital, regardless of age or medical history. Maintaining a broad differential diagnosis and considering PNS early can lead to timely interventions and better outcomes.