Metastatic Papillary Thyroid Carcinoma Unveiled in a Patient with New-Onset Myasthenia Gravis - Thyroid Biology and Disease SAT-327

Q: What symptoms and test results supported the diagnosis of myasthenia gravis in this case?

The patient had ptosis, diplopia, fatigue, and progressive lower-extremity weakness and sensory symptoms that worsened by day’s end and improved with prednisone and pyridostigmine. EMG confirmed MG.

Q: How was metastatic papillary thyroid carcinoma identified despite the initial MG presentation?

Thyroid testing showed subclinical hyperthyroidism, and ultrasound revealed a suspicious hypoechoic nodule with calcifications and cervical lymphadenopathy. FNA confirmed PTC and subsequent thyroid lobectomy with neck dissection showed metastatic involvement of 14/16 lymph nodes.

Q: Why does the report recommend cancer vigilance for patients with new or atypical MG?

The authors note growing evidence of an association between MG and extrathymic malignancies, including PTC, and cite studies suggesting higher cancer incidence and increased risk of extrathymic neoplasms. Immune dysregulation may contribute to both MG and reduced cancer immunosurveillance.

Sep 23, 2026

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A case study links new-onset myasthenia gravis (MG) with metastatic papillary thyroid carcinoma (PTC). A 58-year-old man presented with ptosis, diplopia, fatigue, and progressive sensory and motor symptoms consistent with MG, responding to prednisone and pyridostigmine. MG workup found negative neuropathy and autoimmune panels, while EMG confirmed MG plus neuropathy and carpal tunnel syndrome. Thyroid evaluation showed subclinical hyperthyroidism and imaging suspicious for PTC with cervical lymphadenopathy, confirmed by FNA and surgery. The report emphasizes vigilant cancer screening in atypical or new MG due to higher malignancy risk.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages1

Reading Time3 min

AccessFree to download

Introduction

Case presentation

Clinical presentation and diagnosis

Thyroid evaluation and surgery

Conclusion

A1184 | Journal of the Endocrine Society | [https://doi.org/10.1210/jendso/bvaf149](https://doi.org/10.1210/jendso/bvaf149) Department of Endocrinology, University of Miami, Miami, FL, USA Disclosure: A. Razzeto: None. K. Baez: None. J. Mark: None. C.V. Villabona: None. Introduction: Myasthenia gravis(MG)is associated with thymic abnormalities and autoimmune thyroid diseases, most commonly hyperthyroidism. However, emerging evidence suggests a potential link with thyroid cancer. This case highlights a rare presentation of new-onset MG concurrent with metastatic papillary thyroid carcinoma (PTC) . Case Presentation: A 58-year-old male with a history of hypertension and hyperlipidemia presented with ptosis, diplopia, fatigue, and progressive lower extremity weakness, numbness and tingling exacerbated at the end of the day. Symptoms, highly suggestive of MG, improved with prednisone and pyridostigmine. Evaluation for causes of neuropathy including heavy metals, vitamin deﬁciencies (B12, folate, B6), autoimmune disorders (connective tissue, Sjogren’s, anti-dsDNA), paraneoplastic panel, acetylcholine receptor, and MuSK antibodies were negative. Thyroid tests showed subclinical hyperthyroidism (TSH 0.26 mIU/L, normal free T4 1 . 1 ng/dL) . EMG conﬁrmed MG, peripheral sensory neuropathy, and carpal tunnel syndrome. Imaging studies revealed a 5 mm pituitary microadenoma and a thyroid nodule, without thymic mass. Subsequent thyroid ultrasound revealed a suspicious 1.3 cm hypoechoic nodule with calciﬁcations and cervical lymphadenopathy. FNA of both conﬁrmed PTC. Thyroglobulin was elevated (69 .9 ng/mL), thyroglobulin antibodies negative (< 1.0 IU/mL), TSH normalized (0.8 mcIU/mL) . Left thyroid lobectomy with neck dissection revealed PTC (pT1bN1) with left recurrent laryngeal nerve invasion and metastases to 14/16 lymph nodes. Completion of right thyroid lobectomy is planned. Conclusion: This case adds to the growing evidence of an association between MG and extrathymic malignancies, including PTC. While reported in a small number of cases, studies suggest that patients with MG have an increased cancer incidence of1 .7%-15 .4% vs 2 . 78% in the general population and a 1 . 38-fold higher risk of extrathymic neoplasms. Immune dysregulation may play a role in both MG and reduced cancer immunosurveillance. Therefore, clinicians should be vigilant for potential co-occurring cancers, particularly thyroid carcinoma, in patients presenting with newonset or atypical MG. Presentation: Saturday, July 12, 2025 Abstract citation ID: bvaf149.2245 Thyroid Biology and Disease SAT-327 Metastatic Papillary Thyroid Carcinoma Unveiled ina Patient with New-Onset Myasthenia Gravis Alejandra Razzeto, MD, Karla Baez, Jara Mark, and Carmen Vanessa Villabona, MD J Endocrine Soc, Volume 9, Issue Supplement_ 1, October–November 2025 A1184

FAQs

What symptoms and test results supported the diagnosis of myasthenia gravis in this case?

The patient had ptosis, diplopia, fatigue, and progressive lower-extremity weakness and sensory symptoms that worsened by day’s end and improved with prednisone and pyridostigmine. EMG confirmed MG.

How was metastatic papillary thyroid carcinoma identified despite the initial MG presentation?

Thyroid testing showed subclinical hyperthyroidism, and ultrasound revealed a suspicious hypoechoic nodule with calcifications and cervical lymphadenopathy. FNA confirmed PTC and subsequent thyroid lobectomy with neck dissection showed metastatic involvement of 14/16 lymph nodes.

Why does the report recommend cancer vigilance for patients with new or atypical MG?

The authors note growing evidence of an association between MG and extrathymic malignancies, including PTC, and cite studies suggesting higher cancer incidence and increased risk of extrathymic neoplasms. Immune dysregulation may contribute to both MG and reduced cancer immunosurveillance.

Sep 23, 2026

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