General hyperpigmentation induced by Grave's disease: A case report

Rationale: Hyperpigmentation is a common skin disease. However, there are few reported cases of Grave's disease with diffuse hyperpigmentation. We hereby described a rare case with diffuse hyperpigmentation induced by Grave's disease. Patient concerns: A 42-year-old Chinese woman with accumulated general pigmentation of skin was admitted to our hospital in October 2017. On examination, hyperpigmentation was observed throughout the whole body, especially on the extremities and the face. Diagnoses: The patient has elevated levels of serum free thyroxine (FT4), free triiodothyronine (FT3), reduced levels of thyroid-stimulating hormone (TSH) and positive anti-TSH receptor antibody (TRAb). She presented with grade I goiter and a diffusely increased thyroid uptake to 18.5% in thyroid scan. Histopathological examination demonstrated melanin pigmentation in the pigmented skin area. The patient was diagnosed with hyperpigmentation induced by Grave's disease. Interventions: The patient was treated with oral methimazole (15 mg/day) for thyroid dysfunction and beta blocker for symptom control. Outcomes: After a period of treatment with methimazole and beta blocker, symptoms of hyperthyroidism ameliorated and hyperpigmentation abated. Lessons: Our studies proposed that in this case the diffuse hyperpigmentation in Grave's disease was caused by elevated adrenocorticotropic hormone (ACTH) as well as anti- TSH receptor stimulating antibody instead of enhanced capillary fragility. Other potential mechanisms for skin pigmentation in hyperthyroidism still need further exploration.