Masticatory muscle tendon-aponeurosis hyperplasia that was initially misdiagnosed for polymyositis: a case report and review of the literature

Wataru Katagiri; Daisuke Saito; Satoshi Maruyama; Makiko Ike; Hideyoshi Nisiyama; Takafumi Hayashi; Jun-Ichi Tanuma; Tadaharu Kobayashi

doi:10.1186/s40902-023-00386-6

Masticatory muscle tendon-aponeurosis hyperplasia that was initially misdiagnosed for polymyositis: a case report and review of the literature

Maxillofac Plast Reconstr Surg. 2023 May 1;45(1):18. doi: 10.1186/s40902-023-00386-6.

Authors

Wataru Katagiri¹, Daisuke Saito², Satoshi Maruyama³, Makiko Ike⁴, Hideyoshi Nisiyama⁴, Takafumi Hayashi⁴, Jun-Ichi Tanuma⁵, Tadaharu Kobayashi²

Affiliations

¹ Department of Oral and Maxillofacial Surgery, Gifu University Graduate School of Medicine, Yanagido, Gifu, 501-1194, Japan. w_kat@gifu-u.ac.jp.
² Division of Reconstructive Surgery for Oral and Maxillofacial Region, Faculty of Dentistry & Graduate School of Medical and Dental Science, Niigata University, 2-5274 Gakkocho-dori, Chuo-Ku, Niigata, 951-8514, Japan.
³ Oral Pathology Section, Department of Surgical Pathology, Niigata University Hospital, 1-754 Asahimachi-Dori, Chuo-Ku, Niigata, 951-8520, Japan.
⁴ Division of Oral and Maxillofacial Radiology, Faculty of Dentistry & Graduate School of Medical and Dental Sciences, Niigata University, 2-5274 Gakkocho-Dori, Chuo-ku, Niigata, 951-8514, Japan.
⁵ Division of Oral Pathology, Faculty of Dentistry & Graduate School of Medical and Dental Sciences, Niigata University, 2-5274 Gakkocho-dori, Chuo-Ku, Niigata, 951-8514, Japan.

Abstract

Background: Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is a relatively newly identified clinical condition that manifests as trismus with a square-shaped mandible. Herein, we report a case of MMATH that was initially misdiagnosed for polymyositis due to trismus and simultaneous lower limb pain, with literature review.

Case presentation: A 30-year-old woman had a history of lower limb pain after exertion for 2 years. Initial physical examination had been performed at the Department of General Medicine in our hospital. There was also redness in the hands and fingers. Although polymyositis was suspected, it was denied. The patient visited our department for right maxillary wisdom tooth extraction. Clinical examination revealed that the patient had a square-shaped mandible. The maximal mouth opening was 22 mm. There was no temporomandibular joint pain at the time of opening. Furthermore, there was awareness of clenching while working. Panoramic radiography revealed developed square mandibular angles with flattened condyles. Computed tomography showed enlarged masseter muscles with high-density areas around the anterior and lateral fascia. Magnetic resonance imaging also showed thickened tendons and aponeuroses on the anterior surface and inside bilateral masseter muscles. Finally, the patient was diagnosed with MMTAH. Bilateral aponeurectomy of the masseter muscles with coronoidectomy and masseter muscle myotomy was performed under general anesthesia. The maximum opening during surgery was 48 mm. Mouth opening training was started on day 3 after surgery. Histopathological examination of the surgical specimen showed that the muscle fibers were enlarged to 60 μm. Immunohistochemistry testing for calcineurin, which was associated with muscle hypertrophy due to overload in some case reports, showed positive results. Twelve months after surgery, the mouth self-opening and forced opening were over 35 mm and 44 mm, respectively.

Conclusions: Herein, we report a case of MMATH. Lower limb pain due to prolonged standing at work and overload due to clenching were considered risk factors for symptoms onset of MMATH.

Keywords: Aponeurosis; Calcineurin; Fascia; Hyperplasia; Magnetic resonance imaging; Masticatory muscles; Myotomy; Polymyositis; Square-shaped mandible; Tendons.