Hepatocellular Carcinoma Masquerading as Paraneoplastic Myasthenia Gravis 2219

• Published in: The American journal of gastroenterology Vol. 113; no. Supplement; p. S1260
• Main Authors: Choi, Kati, Sabichi, Anita L., Ramineni, Maheshwari
• Format: Journal Article
• Language: English
• Published: New York Wolters Kluwer Health Medical Research, Lippincott Williams & Wilkins 01.10.2018
• Subjects: Alcohol abuse; Dysarthria; Gastroenterology; Liver cancer; Myasthenia gravis; Tumors
• ISSN: 0002-9270; 1572-0241
• DOI: 10.14309/00000434-201810001-02218

Myasthenia gravis (MG) is an autoimmune neuromuscular junction disease involving the attack of postsynaptic acetylcholine receptors by antibodies that results in fatigable muscle weakness. Paraneoplastic MG in the setting of thymomas is well-described; however, its association with extrathymic malignancies is less common. A 73-year-old retired chemical plant operator with no history of alcohol abuse presented with two months of progressively worsening dysphagia, dysarthria and unintentional weight loss. Neurological examination was notable for bilateral ptosis with positive ice pack test, and dysarthria that worsened with continued conversation suggestive of fatigability. Given that his electromyogram demonstrated decrementing response to repetitive stimulation, elevated serum anti-acetylcholine receptor antibody and favorable response to pyridostigmine, he was diagnosed with myasthenia gravis. In addition to pyridostigmine, he received a five-day course of intravenous immunoglobulin, prednisone and mycophenolate with clinical improvement. Imaging showed no thymoma, but revealed 2 large liver masses with arterial enhancement and venous washout on triple phase CT consistent with hepatocellular carcinoma (HCC). Biopsy of the liver mass was also suggestive of HCC. Further workup revealed negative hepatitis panel, but markedly elevated alpha-fetoprotein to 640 ng/ml (normal <10 ng/mL). Given the large size and location of HCC, it was deemed not amendable to surgery or radioembolization. Sorafenib was offered pending improvement in performance status, and family opted to seek a second opinion at a cancer facility. Outside of thymomas, paraneoplastic MG is less frequent, and for it to be the initial manifestation of HCC is rare. This paraneoplastic syndrome is thought to develop after the production of antibodies against tumor cells that subsequently cross-react with antigens of normal tissue. To date, only 2 cases of paraneoplastic MG from HCC have been published. Aside from adding to the rare cases described in the literature, this case highlights the importance of considering paraneoplastic phenomenon in older patients with risk factors for malignancy who present with new onset MG.