Thymoma is often associated with autoimmune diseases in about one-third of cases [3], although the cases of thymoma associated with alopecia areata are rare. There are reports of alopecia areata in MG-associated thymoma, with a reported incidence of approximately 12%, and the condition does not depend on the degree of MG activity [2]. As MG is a common complication of thymoma, in the current case, a close examination for MG was also performed before surgery. Although MG was ruled out based on the blood test and clinical findings, we performed transsternal extended thymectomy because of the above report and the fact that MG often develops after thymoma surgery [4].

Thymoma complicated with alopecia areata but without MG is very rare. Alopecia areata is an organ-specific autoimmune disease caused by autoimmune T cells against hair follicle tissue [5]. Alopecia areata is characterized by the presence of CD8-positive lymphocyte infiltration in the hair follicle and decreases the patient’s quality of life. Suzuki et al. described alopecia areata as one of the non-motor symptoms of MG-associated thymoma and stated that it may be overlooked for the following reasons [2]; (1) thymoma-associated MG is not a common disease, and few patients are usually followed at a single institution; (2) MG is severe, and other symptoms are unnoted; (3) the neurologist, thoracic surgeon, and dermatologist follow up the patient separately; and (4) in addition to thymectomy, the patient may receive radiotherapy, chemotherapy, or immunotherapy, and thymoma-associated MG may be considered the side effect of these therapies.

Although alopecia areata could improve after thymoma resection, steroid therapy is often used [6]. Yu-Ri et al. reported a case of alopecia areata associated with thymoma without MG, which was improved in three months after surgical removal of a thymoma without steroid therapy [7]. To our best knowledge, this was the second case reported of alopecia areata associated with thymoma without MG. It is impossible to compare whether there is a difference in hair growth after thymectomy between thymoma complicated with MG and without MG, because there are very few reports of alopecia areata associated with thymoma without MG, so we are waiting for more such cases to be accumulated.

In addition, this case has not developed MG in the past or present. We would know when such a case would develop MG, however, to our best knowledge, this is only the second case reported, so we do not know at this time when a case of alopecia areata associated with thymoma without MG complication will develop MG. Further accumulation of cases will be necessary in the future.