Too Weak to Breathe: An Odd Case of Lambert Eaton Myasthenic Syndrome

Abstract

SESSION TITLE: Critical Care 3 SESSION TYPE: Affiliate Case Report Poster PRESENTED ON: Tuesday, October 31, 2017 at 01:30 PM - 02:30 PM INTRODUCTION: Lambert Eaton Myasthenic Syndrome (LEMS) is a rare autoimmune disorder of the neuromuscular junction characterized by the presence of antibodies against voltage gated calcium channels (VGCC) often associated with an underlying neoplasm. CASE PRESENTATION: 52 year old Caucasian female was admitted to an outside hospital with lethargy, shortness of breath and was intubated for acute hypercapnic respiratory failure which ultimately resolved and she was extubated. Her discharge diagnosis was presumed obstructive sleep apnea. Three weeks later she presented to our hospital with the same symptoms. Physical exam was significant for diminished breath sounds bilaterally and musculoskeletal exam was normal on presentation. Arterial blood gas was 7.26/79/118/35 after 30 minutes on non-invasive positive pressure ventilation, prompting intubation. On the ventilator she was awake and alert without sedation, but failed repeated breathing trials due to apnea, low tidal volumes and a negative inspiratory force of -10 cmH2O. Her persistant, profound and unexplained respiratory muscle weakness, raised concerns for a neuromuscular disorder and neurology was consulted. Electromyogram and nerve conduction studies revealed a post exercise increase in compound muscle action potential response > 200%, her VGCC antibodies were positive and acetylcholine receptor antibodies were negative. Computerized Tomography of the chest demonstrated a right suprahilar mass with a paratracheal lymph node which was hypermetabolic on Positron Emission Tomography. Endobronchial Ultrasound with biopsy of the lymph node confirmed small cell lung carcinoma. She was treated with pyridostigmine and plasma exchange with excellent response and was extubated several days later. She received three cycles of etoposide, cisplatin, chest radiation and is currently on mestinon and 3,4 diaminopyridine for her LEMS. DISCUSSION: LEMS classically presents as proximal muscle weakness, autonomic dysfunction and areflexia. Respiratory failure is a common primary manifestation of Myasthenia Gravis, however the literature rarely documents LEMS as presenting this way. This case highlights the importance of considering occult neuromuscular diseases in cases of unexplained respiratory failure even if other classical symptoms such as muscle weakness are absent. Our patient had repeated episodes of respiratory failure requiring intubation that was initially misdiagnosed, leading to missed treatment opportunities, a poor quality of life and an unchecked pulmonary malignancy. CONCLUSIONS: LEMS often presents early in the neoplastic course, thus diagnosis has important implications. Treatment of LEMS can be effective in relieving the neuromuscular symptoms and early detection of the underlying malignancy can be lifesaving. Reference #1: Fatima. U., Shah. T., Dedhia.P., Devine. S., Lambert Eaton Syndrome: Unique Presentation of the Disease with Isolated Respiratory Muscle Weakness. CHEST. Abstract 326A. October 2013. DISCLOSURE: The following authors have nothing to disclose: Caryn Brehm, Christopher Barrios, James Caress, Daniel Files, Daniel LoVerde No Product/Research Disclosure Information