Thymic hyperplasia associated with
Graves' disease is rarely reported in children, although it is not uncommon in adults. Occasionally, an enlarged thymus presents as an anterior mediastinal mass on a radiographic examination. Such patients often undergo invasive procedures such as a thymus biopsy or
thymectomy because of suspected
malignancy. However, an enlarged thymus with
Graves' disease is known to shrink
after treatment with
antithyroid drugs. Therefore, recognition of this benign course would avoid unnecessary surgical resection. This report presents the case of a 10-yr-old boy with
Graves' disease complicated with an anterior mediastinal mass. Computed tomography showed a homogenous mass with no invasion into the surrounding tissue. A
gallium-67 scintigraphy showed no abnormal uptake. Shrinkage of the mass
after treatment with an
antithyroid drug (methyl-mercaptoimidazole) supported the diagnosis of
thymic hyperplasia with
Graves' disease. This case report illustrates two important points. First, pediatricians should be aware that
thymic hyperplasia can coexist with
Graves' disease, even in children. Second, close radiographic assessment would support a diagnosis of
thymic hyperplasia and eliminate invasive diagnostic procedures.