A RARE CASE OF SYMPTOMATIC LOW-GRADE DAPSONE-INDUCED METHEMOGLOBINEMIA: A CASE REPORT

Abstract

SESSION TITLE: Medical Student/Resident Pharmacotherapeutics SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 PM - 02:15 PM INTRODUCTION: Methemoglobinemia is a life-threatening condition that can be difficult to diagnose. Acquired methemoglobinemia is an uncommon condition, caused by a variety of exogenous agents such as dapsone. It results in a saturation gap between oxygen saturation on pulse oximetry and arterial blood gas analysis. Most patients are asymptomatic on the lower levels and manifest symptoms at the higher level, i.e., more than 25%. We present a rare case of symptomatic low-grade methemoglobinemia with severe fluctuations in symptoms and levels even with aggressive management with intravenous methylene blue, oral ascorbic acid, and oral cimetidine. CASE PRESENTATION: A 24-year-old female with a past medical history significant for angioedema on omalizumab and prednisone presented with lightheadedness, near syncope, exertional dyspnea, and cyanosis. She has a history of recurrent angioedema, with multiple relapses, stable on prednisone and omalizumab. Her immunologist recently added dapsone to wean her off from chronic steroids. In ER, her vitals were: BP 123/60, HR 123, pulse oximetry showed 91% on 2 liters of oxygen. Physical examination was unremarkable except mild cyanosis. Orthostatic were negative. Labs showed Cr 0.6, BUN 12.0, Hemoglobin of 12 and normal electrolytes. She walked to the restroom and desatted to low 70s and became severely out of breath. She was started on high flow nasal cannula. Further investigation confirmed a diagnosis of methemoglobinemia with a level of 15.6%. As she was symptomatic, she received a dose of intravenous methylene blue (MB). Her condition improved and repeated methemoglobin 4.9% after 16 hours. In next 10 hours, she had similar symptoms with the repeated level of 16.9%. A second dose of IV methylene blue was delivered. At the same time, oral cimetidine and ascorbic acid were started that resulted in improvement of symptoms. Next day, she had similar worsening of the symptoms with elevated levels followed by receiving the third dose of intravenous methylene blue. Her hospital course was complicated by an episode of angioedema, managed with IV steroids and epinephrine. She had persistent tachycardia in spite of normal ABGs. She was transferred to tertiary care center on her request where was given a blood transfusion and discharge to home to follow up with her immunologist. She was advised not to take dapsone. Her condition improved over time. DISCUSSION: An interesting case with low grade symptomatic, and severe fluctuation of symptoms and methemoglobin levels even with management with IV methylene blue, oral ascorbic acid, and cimetidine was reported. CONCLUSIONS: Methemoglobinemia is a rare diagnosis when patients present with cyanosis and other features of hypoxia that are unrelated to cardiopulmonary causes. It is a life-threatening condition that can be difficult to diagnose. Reference #1: Barclay JA , Ziemba SE , Ibrahim RB . Dapsone-induced methemoglobinemia: a primer for clinicians . Ann Pharmacother 2011 ;45 : 1103 – 1115 . Reference #2: Tracqui A, Gutbub AM, Kintz P, Mangin P (1995) A case of acute dapsone poisoning: toxicological data and review of the literature. J Anal Toxicol 19:229–235 DISCLOSURES: No relevant relationships by Abdul Aleem, source=Web Response No relevant relationships by Mohammad Yousuf, source=Web Response