Pregnancy in Autoimmune Polyglandular Syndrome Type 3c With Graves’ Disease and Myasthenia Gravis: A Case Report

Autoimmune polyglandular syndrome type 3c (APS3c), characterized by autoimmune thyroid disease with another organ-specific autoimmune disorder in the absence of adrenal insufficiency, is an uncommon presentation.Its coexistence with Graves' disease and myasthenia gravis (MG) is rare and poses additional diagnostic and therapeutic challenges, particularly when complicated by thyroid storm and pregnancy.We report the ongoing management of a 22-year-old woman with this combination of autoimmune disorders.She was admitted with thyroid storm diagnosed using the Burch-Wartofsky Point Scale and Japan Thyroid Association criteria after a 15-month history of weight loss, heat intolerance, diaphoresis, anxiety, palpitations, unilateral ptosis, and fatigable proximal upper-extremity weakness.Graves' disease and MG were diagnosed based on clinical findings, positive thyroid-stimulating immunoglobulin and acetylcholine receptor antibodies, and electrophysiological evidence of a postsynaptic neuromuscular junction disorder.In the absence of clinical or biochemical evidence of primary adrenal insufficiency, the coexistence of autoimmune thyroid disease and MG supported a diagnosis of APS3c on the Neufeld and Blizzard classification.Despite methimazole (15 mg/day) and pyridostigmine (600 mg/day) therapy, and good adherence to treatment, biochemical hyperthyroidism persisted and progressed to thyroid storm.During outpatient follow-up, an intrauterine pregnancy was confirmed.Methimazole was withheld during the first trimester while the patient remained clinically stable despite persistent biochemical hyperthyroidism, and it was resumed thereafter.At the time of writing, the pregnancy remains ongoing under multidisciplinary care involving endocrinology, neurology, internal medicine, and maternal-fetal medicine, with serial maternal monitoring, planned third-trimester antibody reassessment, targeted fetal ultrasonography, perinatal planning, and neonatal surveillance.This case highlights APS3c as an important diagnostic framework for the coexistence of Graves' disease and MG and illustrates how management must be continually reassessed in the setting of thyroid storm and pregnancy.Maternal, fetal, and neonatal outcomes remain pending.