A CASE OF SUSPECTED LIMB-GIRDLE MUSCULAR DYSTROPHY WITH SEVERE NOCTURNAL HYPOXIA

Abstract

SESSION TITLE: Complications You Don't Want to Miss SESSION TYPE: Fellow Case Reports PRESENTED ON: 10/10/2018 10:45 AM - 11:45 AM INTRODUCTION: Limb-girdle muscular dystrophy (LGMD) describes a rare group of heterogeneous genetic mutations that result in myopathies of proximal muscles. CASE PRESENTATION: A 40-year-old man with a past medical history of substance abuse (alcohol, amphetamine) and heavy use of oral bodybuilding supplements developed progressive proximal muscle weakness in 2 years. During this time, he survived a cardiac arrest for which diagnostic workup revealed non-ischemic dilated cardiomyopathy with an ejection fraction of 25% and new-onset atrial fibrillation. Physical examination confirmed a limb-girdle pattern of weakness and bilateral gastrocnemius muscle hypertrophy. These findings, along with an elevated CK level of 2630 and adult-onset cardiac abnormalities, were suspicious for a diagnosis of LGMD. Comprehensive muscular dystrophy genetic testing panel was negative, and a biopsy of his deltoid muscle showed necrotizing myopathy and thus was non-specific. ANA was positive at 1:160, and spirometry at this time showed a restrictive pattern consistent with neuromuscular disease (FVC = 2.64L [61% predicted], FEV1/FVC = 86%, MIP = -90 cmH2O, ETCO2 = 46 mmHg). A split-night polysomnophraphy (PSG) was performed: Apnea Hypopnea Index (AHI) = 31 events per hour (normal < 5) without central apneic events or Cheyne-Stokes breathing; Oxygen Desaturation Index (ODI) = 64 events per hour (normal < 5); Lowest SpO2 = 70%; Amount of sleep time SpO2 < 90% = 33.3%; Maximum TcCO2 = 41.2 mmHg. Due to the severity of sleep-disordered breathing and significant hypoxemia, he was prescribed nocturnal bi-level ST non-invasive ventilation but he was not able to tolerate. In the following months, his proximal strength subjectively improved spontaneously. Pulmonary function testing showed improvement: FVC = 2.88L (79% predicted), FEV1/FVC = 88%, MIP = -84 cmH2O. Furthermore, overnight oximetry without non-invasive ventilation showed improvement of his nocturnal hypoxia: Lowest SpO2 = 88%; Mean SpO2 = 97.5%; Amount of sleep time SpO2 < 88% = 0%; ODI = 4.9 events per hour. DISCUSSION: Current treatment for LGMD remains supportive with physical therapy, treatment of cardiomyopathy (if present) and nocturnal non-invasive ventilation for neuromuscular respiratory weakness. Prevalence estimates range from 1 in 14,500 to 1 in 123,000 individuals. This case is atypical in that no genetic mutation has been identified to confirm diagnosis of LGMD, and that the patient's strength, spirometry data, and degree of nocturnal hypoxia spontaneously improved. CONCLUSIONS: Especially in patients with neuromuscular disease associated with cardiomyopathy and neuromuscular respiratory weakness, it is important to identify nocturnal respiratory impairment and characterize sleep-disordered breathing patterns. This may impact timing of non-invasive ventilation initiation and which device and mode of non-invasive positive-pressure ventilation to prescribe. Reference #1: Aboussouan LS, Mireles-Cabodevila E. Sleep-Disordered Breathing in Neuromuscular Disease: Diagnostic and Therapeutic Challenges. Chest 2017;152(4):880-892 Reference #2: Wolfe LF, Joyce NC, McDonald CM, Benditt JO, Finder J. Management of pulmonary complications in neuromuscular disease. Phys Med Rehabil Clin N Am. 2012;23(4):829-53 Reference #3: Wicklund MP, Kissel JT. The limb girdle muscular dystrophies. Neurol Clin 2014;32(3):729-49 DISCLOSURES: No relevant relationships by Michelle Cao, source=Web Response No relevant relationships by Halley Tsai, source=Web Response