Idiopathic intrinsic contracture (IIC) with no history of trauma, ischemia, or spasticity is extremely rare. We report herein a case of impaired extension of the digits due to bilateral IICs occurred in a 30-year-old woman with a past medical history of eating disorder and amenorrhea. Although no previous case has been reported in the literature, eight similar cases of IIC have been presented at Japanese domestic conferences. In these eight cases and the present case, resection of the thenar muscle cords and unilateral resection of the lateral band were effective. Since IIC in patients with an eating disorder is a rare condition, it would be treated conservatively at first as tendon sheath inflammation or locking. However, this condition may be resistant to conservative treatment, and surgical treatment should be considered in such cases.