Rationale: With the absence of ophthalmopathy, thyroid dermopathy especially lesions at atypical locations is a very rare presentation. We herein report an original case of bilateral breast myxedema caused by Grave's disease. Patient concerns: A 21-year-old unmarried woman presented with a 4-month history of Grave's disease and a 1-month history of progressive bilateral breast enlargement. She had symmetrical bilateral breast enlargement with redness and nonpitting thickening of the skin, diffusely enlarged thyroid glands, and no exophthalmos. Diagnosis: Ultrasonography, magnetic resonance imaging scan, and skin biopsy confirmed the diagnosis of bilateral breast myxedema. Interventions: The patient was treated with multipoint subcutaneous injections of triamcinolone acetonide in each breast every month. Outcomes: The bilateral breast returned approximately to its normal size after therapy for 6 months. Conclusions: Our case illustrates that multipoint subcutaneous injection of glucocorticoids is beneficial for bilateral breast myxedema.