Clinicopathologic Features of Oculopharyngodistal Myopathy With <i>LRP12</i> CGG Repeat Expansions Compared With Other Oculopharyngodistal Myopathy Subtypes
Authors: Theerawat Kumutpongpanich, Masashi Ogasawara, Ayami Ozaki, Hiroyuki Ishiura, Shoji Tsuji, Narihiro Minami, Shinichiro Hayashi, Satoru Noguchi, Aritoshi Iida, Ichizo Nishino, Madoka Mori-Yoshimura, Yasushi Oya, Kenjiro Ono, Toshio Shimizu, Akihiro Kawata, Shun Shimohama, Keiko Toyooka, Kaoru Endo, Shuta Toru, Oga Sasaki, Kenji Isahaya, Masanori P. Takahashi, Kazuo Iwasa, Jun-Ichi Kira, Tatsuya Yamamoto, Michi Kawamoto, Tadanori Hamano, Kazuma Sugie, Nobuyuki Eura, Tomo Shiota, Mizuho Koide, Kanako Sekiya, Hideaki Kishi, Takuto Hideyama, Shigeru Kawai, Satoshi Yanagimoto, Hiroyasu Sato, Hajime Arahata, Shigeo Murayama, Kayoko Saito, Hideo Hara, Takashi Kanda, Hiroshi Yaguchi, Noboru Imai, Yuichi Kawagashira, Mitsuru Sanada, Kazuki Obara, Misako Kaido, Minori Furuta, Takashi Kurashige, Wataru Hara, Daisuke Kuzume, Mamoru Yamamoto, Jun Tsugawa, Hitaru Kishida, Naoki Ishizuka, Kohei Morimoto, Yukio Tsuji, Atsuko Tsuneyama, Atsuhiro Matsuno, Ryo Sasaki, Daigo Tamakoshi, Erika Abe, Shinichiro Yamada, Akiyuki Uzawa
Journal: JAMA Neurology (2021)

<h3>Importance</h3> Repeat expansion of CGG in<i>LRP12</i>has been identified as the causative variation of oculopharyngodistal myopathy (OPDM). However, to our knowledge, the clinicopathologic features of OPDM with CGG repeat expansion in<i>LRP12</i>(hereafter referred to as OPDM_LRP12) remain unknown. <h3>Objective</h3> To identify and characterize the clinicopathologic features of patients with OPDM_LRP12<i>.</i> <h3>Design, Setting, and Participants</h3> This case series included 208 patients with a clinical or clinicopathologic diagnosis of oculopharyngeal muscular dystrophy (OPDM) from January 1, 1978, to December 31, 2020. Patients with GCN repeat expansions in<i>PABPN1</i>were excluded from the study. Repeat expansions of CGG in<i>LRP12</i>were screened by repeat primed polymerase chain reaction and/or Southern blot. <h3>Main Outcomes and Measures</h3> Clinical information, muscle imaging data obtained by either computed tomography or magnetic resonance imaging, and muscle pathologic characteristics. <h3>Results</h3> Sixty-five Japanese patients with OPDM (40 men [62%]; mean [SD] age at onset, 41.0 [10.1] years) from 59 families with CGG repeat expansions in<i>LRP12</i>were identified. This represents the most common OPDM subtype among all patients in Japan with genetically diagnosed OPDM. The expansions ranged from 85 to 289 repeats. A negative correlation was observed between the repeat size and the age at onset (<i>r</i><sup>2</sup> = 0.188,<i>P</i> = .001). The most common initial symptoms were ptosis and muscle weakness, present in 24 patients (37%). Limb muscle weakness was predominantly distal in 53 of 64 patients (83%), but 2 of 64 patients (3%) had predominantly proximal muscle weakness. Ptosis was observed in 62 of 64 patients (97%), and dysphagia or dysarthria was observed in 63 of 64 patients (98%). A total of 21 of 64 patients (33%) had asymmetric muscle weakness. Aspiration pneumonia was seen in 11 of 64 patients (17%), and 5 of 64 patients (8%) required mechanical ventilation. Seven of 64 patients (11%) developed cardiac abnormalities, and 5 of 64 patients (8%) developed neurologic abnormalities. Asymmetric muscle involvement was detected on computed tomography scans in 6 of 27 patients (22%) and on magnetic resonance imaging scans in 4 of 15 patients (27%), with the soleus and the medial head of the gastrocnemius being the worst affected. All 42 muscle biopsy samples showed rimmed vacuoles. Intranuclear tubulofilamentous inclusions were observed in only 1 of 5 patients. <h3>Conclusions and Relevance</h3> This study suggests that OPDM_LRP12 is the most frequent OPDM subtype in Japan and is characterized by oculopharyngeal weakness, distal myopathy that especially affects the soleus and gastrocnemius muscles, and rimmed vacuoles in muscle biopsy.