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Kearns-Sayre Syndrome Cardiovascular and Metabolic Science Clinical case Vol. 31 No. 1 January-March 2020 An uncommon cause of atrioventricular block in young patients: Kearns-Sayre syndrome Una causa infrecuente de bloqueo auriculoventricular en pacientes jóvenes: síndrome de Kearns-Sayre Verónica Posada-Vélez,* Andrés Gómez,‡ Juan Carlos Díaz,§,||,¶,**,‡‡ Julián Aristizábal,§,||,¶,**,‡‡ Jorge Marín,||,¶,‡‡ Jorge Velásquez,§,||,¶,**,‡‡ William Uribe,¶,** Mauricio Duque¶ Keywords: Kearns-Sayre ABSTRACT RESUMEN syndrome, chronic progressive external Kearns-Sayre syndrome (KSS) is a rare cause of complete El síndrome de Kearns-Sayre (SdKS) es una causa ophthalmoplegia, atrioventricular (AV) block in young patients. This infrecuente de bloqueo auriculoventricular (AV) blepharoptosis, heart disorder is caused by mitochondrial DNA (mtDNA) en personas jóvenes. Este desorden es causado por block, mitochondrial deletions, and unlike other mitochondrial diseases, deleciones del ADN mitocondrial (ADNmt), y a diferencia myopathy. involvement of the cardiac conduction system is frequent. de otras enfermedades mitocondriales, el compromiso del KSS is characterized by the triad of progressive external sistema de conducción eléctrica cardiaca es frecuente. Palabras clave: ophthalmoplegia, pigmentary retinopathy and cardiac El SdKS se caracteriza por la triada de oftalmoplejía Síndrome de conduction system disturbances, with an onset before progresiva externa, retinopatía pigmentaria y alteraciones Kearns-Sayre, 20 years of age. We present a case of complete AV block en la conducción eléctrica cardiaca, con síntomas que, oftalmoplejía externa due to this rare condition, which was diagnosed with a por lo general, inician antes de los 20 años de edad. crónica progresiva, muscular biopsy taken at the time of pacemaker implant. Presentamos un caso de bloqueo AV completo debido blefaroptosis, bloqueo a esta rara condición, la cual se diagnosticó mediante cardiaco, miopatía una biopsia muscular tomada al momento del implante mitocondrial. de marcapasos. * Médica Internista, INTRODUCTION prevalence of 1.6 per 100.000 adults), cardiac Universidad CES. ‡ Fellow de involvement is the most important factor in Electrofisiología y trioventricular block (AV) in young adults prognosis and cardiac conduction disturbances Arritmias Cardiacas, Ais infrequent, with non-ischemic heart have an unpredictable rate of progression Universidad CES. disease (mainly myocarditis) accounting for a to complete AV block.3,4 Mortality has been § Cardiología y Electrofisiología, significant percentage of patients. Nonetheless, reported in up to 20% of patients, hence an early Hospital General de most patients don’t have structural anomalies diagnosis could potentially modify prognosis.5 Medellín. or underlying diseases readily identifiable, and We present a case of a patient with || Cardiología y ultimately undergo pacemaker implant without blepharoptosis, paralysis of the extraocular Electrofisiología, 1 Clínica Las Vegas. a clear diagnosis. muscles and complete heart block, in which ¶ Cardiología y Kearns-Sayre syndrome (KSS) is a specific a diagnosis of KSS was made with a muscular Electrofisiología, mitochondrial myopathy caused by large- biopsy taken at the time of permanent Clínica CES. scale deletionwww.medigraphic.org.mx of mitochondrial DNA (mtDNA) pacemaker implant. ** Cardiología y Electrofisiología, which is thought to occur somatically during Clínica Somer. early embryogenesis in the majority of cases. CASE PRESENTATION ‡‡ Cardiología y It typically presents as external progressive Electrofisiología, ophtalmoplegia, pigmentary rethinopathy and A 22-year-old male with a previous history of Clínica Las Américas. various degrees of AV block, usually before bilateral blepharoptosis and external progressive Antioquia, Colombia. 20 years of age.2 Although rare (estimated ophtalmoplegia presented to the emergency Cardiovasc Metab Sci 2020; 31 (1): 25-29 www.medigraphic.com/cms 26 Posada-Vélez V et al. An uncommon cause of atrioventricular block in young patients: Kearns-Sayre syndrome Received: department for syncope which was preceded examination revealed a conscious, alert and 20/10/2019 by several hours of dizziness and diaphoresis. oriented patient with complete bilateral Accepted: 06/04/2020 He reported a reduction in his exercise capacity ophtalmoplegia and blepharoptosis (Figure over the previous 4 months, and presyncope 2 1) without involvement of the lower cranial weeks before the present event. nerves and preserved extremity movement On examination, his heart rate was 38 bpm. and sensibility. His initial electrocardiogram There was no respiratory distress and heart and (ECG) revealed a complete AV block with a respiratory sounds were normal. Neurologic junctional escape rhythm (Figure 2). He had been previously examined by a neurologist as an outpatient, with magnetic resonance imaging (MRI) of the brain revealing brainstem and thalamus atrophy with prominent sulcus. A previously performed spinal tap reported increased protein concentration. No other members of his family had similar symptoms. Due to his complete heart block, the patient was scheduled for dual-chamber pacemaker implant. Given his clinical presentation, a Figure 1: Bilateral blepharoptosis. Although the patient is fully awake, significant mitochondrial myopathy was suspected and ptosis of the upper eyelids is observed. The patient had difficulty with his everyday a muscle biopsy from his pectoralis major activities due to loss of vision caused by his bilateral ptosis. muscle was taken during the procedure. Light microscopy reported the presence of atrophic muscle fibers with ragged red muscle fibers. There were no inflammatory infiltrates, increase in endomysial collagen or glycogen deposits. High resolution optical microscopy reported subsarcolemic and intermyofibrillar mitochondrial accumulation, most of which were increased in size while others were swollen, with abnormal rigid crests or in circular arrangement. Paracrystallin inclusions («parking lot» type) and electrodense bodies were identified. These findings were all compatible with a mitochondrial myopathy (Figure 3). Based on his clinical presentation (bilateral blepharoptosis, external progressive ophtalmoplegia and complete heart block), his brain MRI findings and the results of his muscle biopsy, a diagnosis of Kearns-Sayre syndrome was made and coenzyme Q10 supplementation was initiated. Six months after pacemaker implant, the patient has had improvement in his exercise capacity and no www.medigraphic.org.mxfurther syncope. DISCUSSION Kearns-Sayre syndrome (KSS) is a specific mitochondrial myopathy characterized by Figure 2: Initial ECG demonstrating complete heart block with a junctional escape progressive external ophtalmoplegia, pigmentary rhythm. retinopathy and cardiac conduction system Cardiovasc Metab Sci 2020; 31 (1): 25-29 www.medigraphic.com/cms Posada-Vélez V et al. An uncommon cause of atrioventricular block in young patients: Kearns-Sayre syndrome 27 A B Figure 3: Muscle biopsy: A) Hematoxilin-eosin muscular study C D without remarkable findings.B) Trichrome staining (arrow points subsarcolemmal sarcomere). C and D) High resolution microscopy (note swollen mitochondria with paracrystalline 2 µm 1 µm inclusions). disturbances. Although it is a mitochondrial mutations, including Leber hereditary optic disease, it is rarely due to maternal inheritance neuropathy (LHON); mtDNA-associated and most cases are caused by de-novo large- Leigh syndrome (LS); neuropathy, ataxia and scale deletions (1.3 to 10 kb) of mitochondrial retinitis pigmentosa (NARP); mitochondrial DNAEste documento (mtDNA), es elaborado which poroccur Medigraphic somatically in encephalopathy, lactic acidosis and stroke-like the early embryogenesis period resulting in episodes (MELAS), and myoclonic epilepsy impaired cellular oxidative phosphorylation. with ragged-red fibres (MERRF). In fact, Symptom onset occurs before 20 years of mitochondrial diseases have an estimated age, and patients usually exhibit cerebellar prevalence of 9.2 to 16.5 in 100,000 adults, ataxia, heart block, increased cerebrospinal with asymptomatic mtDNA mutations occurring fluid protein concentration, short stature 1 in 200 to 250 persons.8 While cardiac and multiple endocrine conditions including conduction system anomalies are uncommon diabetes mellitus, hypoparathyroidism or in other mitochondrial diseases, cardiac Addison disease.2,5 As in our case, ophthalmic manifestations (including syncope, heart failure manifestations in KSS precede cardiac and cardiac arrest) occur in as many as 50% of complications and the presence of these may patients with KSS. Magnetic resonance imaging be sufficient to suspect the syndrome and has demonstrated frequent subclinical cardiac actively searchwww.medigraphic.org.mx for cardiac involvement and involvement, even in patients with normal confirmation of the diagnosis.6 Clinical course echocardiograms.2,7 In fact, cardiac involvement is progressive, with mortality occurring between is the most important factor in prognosis, with the third and fourth decade of life, usually due conduction disturbances frequently involving to cardiovascular events (sudden death).2,7 the distal His bundle and bundle branches.9 In addition to KSS, several other syndromes KSS patients undergoing electrophysiological have been described in patients with mtDNA studies typically show normal sinus node Cardiovasc Metab Sci 2020; 31 (1): 25-29 www.medigraphic.com/cms 28 Posada-Vélez
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