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Show Clinical Correspondence Section Editors: Robert Avery, DO Karl C. Golnik, MD Caroline Froment, MD, PhD An-Guor Wang, MD Slowly Progressive Ophthalmoplegia as a Presenting Symptom of Myotonic Dystrophy Type 1 Seunghee Na, MD, Eek-Sung Lee, MD, PhD, Young-Do Kim, MD, PhD, Tae-Kyeong Lee, MD, PhD M yotonic dystrophy Type 1 (DM1) is an autosomal dominant disorder caused by expansion of cytosine– thymine–guanine (CTG) triplet repeats within the dystrophia myotonica protein kinase (DMPK) gene on chromosome 19 (1). Because DM1 affects both skeletal and smooth muscles, patients with DM1 manifest various symptoms, including ocular, cardiac, gastrointestinal tract, and endocrine system impacts. Cataract and myotonia are common presenting symptoms, and patients with small expansion of CTG triplet repeats (mild DM1) may show only these symptoms and have a normal lifespan (1). External ophthalmoplegia is rarely reported as an early sign of DM1 relative to limb weakness. In this article, we report a patient with DM1 who manifested chronic progressive ophthalmoplegia as a presenting symptom. A 51-year-old man presented with progressive painless ophthalmoplegia and bilateral ptosis lasting more than 2 years. The ocular symptoms did not fluctuate and had progressed slowly. His history was unremarkable, except cataract surgery in both eyes 8 months previous. He denied any family history of neurological disorders. On neurologic examination, the patient’s face demonstrated atrophy of the temporalis muscles (Fig. 1). He also showed bilateral incomplete ptosis (i.e., interpalpebral fissure measured 6/6 mm) and exotropia in the left eye in the primary position. The right and left pupils were anisocoric (3 and 4 mm, respectively), with an oval irregular shape of the left one. The pupils were reactive during the light reflex assessment but slightly sluggish. He demonstrated limitations of adduction and supraduction of the left eye and a limitation of supraduction of the right eye (Fig. 2). He showed saccadic pursuit and saccades were hypometric with relatively normal velocity within the limited range of motion. The other cranial nerves were unremarkable. Although he complained of subjective weakness of his hands, an examination revealed no weakness. Meanwhile, the deep tendon reflexes were hypoactive, and there was no handgrip myotonia or percussion myotonia of the limb and trunk muscles. However, mild percussion myotonia of the tongue was observed. Laboratory tests revealed that the serum concentrations of free T4, thyroid-stimulating hormone, antithyroid antibodies, and antiacetylcholine receptor antibodies were within normal limits. Brain MRI findings were normal, and electromyography showed typical myotonic discharges in the right proximal and distal limb muscles and masseter. Genetic testing for DM1 confirmed the presence of a greater-than-150 CTG triplet expansion in the DMPK gene. Our patient with progressive bilateral ptosis and ophthalmoplegia was eventually diagnosed with DM1. His “hatchet face” and history of cataracts were clues that led to our suspicion of DM1, despite the absence of a family history. Several reports have described neuroophthalmologic manifestations of DM1. In such instances, the pupil becomes miotic, and the light reflex turns sluggish as the disease progresses (2). Another report revealed that saccades were usually slow, but the latency and accuracy of saccades did not change significantly, and the smooth pursuit gain was normal in DM1. The maximum velocity of saccades was shown to be correlated with limb muscle Department of Neurology (SN, Y-DK), Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea; and Department of Neurology (E-SL, T-KL), Soonchunhyang University College of Medicine, Bucheon, Korea. Supported by the Soonchunhyang University Research Fund. The authors report no conflicts of interest. Ethical standards: The authors declare that this single case report has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. Address correspondence to Tae-Kyeong Lee, MD, PhD, Department of Neurology, College of Medicine, Soonchunhyang University, Soonchunhyang University Bucheon Hospital, 170 Jomaru-ro, Wonmi-gu, Bucheon 14584, Korea; E-mail: xorudoc@schmc.ac.kr Na et al: J Neuro-Ophthalmol 2021; 41: e741-e742 FIG. 1. The face. The patient’s face showed temporalis atrophy (arrow), that is, “hatchet face.” e741 Copyright © North American Neuro-Ophthalmology Society. Unauthorized reproduction of this article is prohibited. Clinical Correspondence FIG. 2. The 9-gaze photograph. Physical examination revealed bilateral ptosis, limitations of adduction and supraduction in the left eye, and a limitation of supraduction in the right eye. weakness (2). Moreover, myotonia and a warm-up phenomenon were seen during repetitive visually guided saccades (3). The clinical spectrum of DM1 can be classified into 5 types according to onset age and clinical characteristics: congenital, infantile, juvenile, adult, and late onset (1). The later is the age of onset, the less severe is the muscle weakness. Patients with late onset DM1 usually experience disease onset after 40 years of age and show high frequency of cataract, diabetes, obesity, and less severe muscle weakness. In general, DM1 predominantly affects the limb skeletal muscles and cardiac muscles and spares the extraocular muscles. Thus, presenting symptoms can be minimal in patients with late onset DM1, in which ocular findings are usually subtle. External ophthalmoplegia in patients with DM1 has been reported in a few cases (4). DM1 patients with ophthalmoplegia may experience gait disturbance, dysarthria, and prominent percussion myotonia more than 10 years before development of oculomotor disturbance. Thus, ophthalmoplegia in these patients can be considered a subsidiary feature as the disease progresses. On the other hand, Thiries et al reported a patient with DM1 who manifested ophthalmoplegia as the presenting feature and showed only 73 CTG repeats of the DMPK gene (5). The patient did not display any findings of percussion myotonia, weakness, or hatchet face, but there were clues that she had undergone cataract surgery at the age of 38 years, and her cousin had been diagnosed with DM1. The extraocular muscles are different from the skeletal and cardiac muscles for morphological and histological features and gene expression (6). The differentially expressed genes can determine the key features of extraocular muscles and might be why extraocular muscles are differently affected by this genetic disorder relative to limb skeletal muscles. It is known that common etiologies of chronic ophthalmoplegia are chronic progressive external ophthalmoplegia (CPEO), myasthenia gravis, and thyroid ophthalmopathy. In this case, DM1 was diagnosed while investigating the cause of chronic ophthalmoplegia. The e742 ophthalmoplegia pattern of DM1 is similar to that of CPEO. Thus, it will be helpful to infer the etiology by noting associated symptoms such as tongue myotonia and percussion myotonia, hatchet face (temporalis muscle wasting), history of cataracts with an unusually young onset age, and family history of DM1. Once DM1 is suspected as the cause, electromyography will be performed and may reveal myotonic discharges even in cases without prominent skeletal muscle weakness and offer a decisive clue for diagnosis. Therefore, physicians should consider DM1 as a potential cause of progressive ophthalmoplegia and try to detect any minimal neurologic abnormalities. STATEMENT OF AUTHORSHIP Category 1: a. Conception and design: S. Na and T.-K. Lee; b. Acquisition of data: S. Na and Y.-D. Kim; c. Analysis and interpretation of data: S. Na and Y.-D. Kim. Category 2: a. Drafting the manuscript: S. Na; b. Revising it for intellectual content: E.-S. Lee and T.-K. Lee. Category 3: a. Final approval of the completed manuscript: T.-K. Lee. REFERENCES 1. De Antonio M, Dogan C, Hamroun D, Mati M, Zerrouki S, Eymard B, Katsahian S, Bassez G; French Myotonic Dystrophy Clinical Network. Unravelling the myotonic dystrophy type 1 clinical spectrum: a systematic registry-based study with implications for disease classification. Rev Neurol (Paris). 2016;172:572–580. 2. Ter Bruggen JP, Tijssen C, Bastiaensen L. Myotonic dystrophy: the natural history of eye movement disorders. Neuroophthalmology. 1993;13:85–88. 3. Versino M, Rossi B, Beltrami G, Sandrini G, Cosi V. Ocular motor myotonic phenomenon in myotonic dystrophy. J Neurol Neurosurg Psychiatry. 2002;72:236–240. 4. Lessell S, Coppeto J, Samet S. Ophthalmoplegia in myotonic dystrophy. Am J Ophthalmol. 1971;71:1231–1235. 5. Thiriez C, Vignal C, Papeix C, Yaici S, Vidailhet M, Roze E. Ophthalmoplegia as the presenting muscle-related manifestation of myotonic dystrophy. Rev Neurol (Paris). 2010;166:538–541. 6. Spencer R, Porter D. Biological organization of the extraocular muscles. Prog Brain Res. 2006;151:43–80. Na et al: J Neuro-Ophthalmol 2021; 41: e741-e742 Copyright © North American Neuro-Ophthalmology Society. 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