eng Science and Education Publishing American Journal of Medical Case Reports 2374-216X 2023-02-05 11 2 19 22 10.12691/ajmcr-11-2-3 AJMCR20231123 article Dov Vachss 1 Yasna Yusuf 1 Dylan Bobrow 1 Patrick Geraghty Patrick.Geraghty@downstate.edu 1 Department of Medicine, State University of New York Downstate Health Sciences University, 450 Clarkson Avenue, Brooklyn, NY 11203, USA Lyme disease is a vastly underdiagnosed disease, and its frequency is steadily rising. It is commonly diagnosed clinically and treated empirically, due to the time required for testing and the inefficiency of laboratory testing methods. Although there are a few reported cases of Lyme carditis, the variation in the clinical presentation and the treatment provided differ significantly. Herein, we present the case of a man who presented in July 2022 with a non-productive cough and low-grade fever along with mild body aches. The patient had an incidental atrial flutter with a 2:1 atrioventricular block, a large thick-walled cavitary lesion in the apex of the left lung, left upper lobe ground-glass opacities, and scattered micronodules in the left lower lobe. He was clinically diagnosed with Lyme carditis despite testing negative for Lyme antibodies. This was in combination with Pseudomonal pneumonia. Here we review recent cases of Lyme carditis and discuss the difficulty of the efficiency of serological testing for Lyme disease. http://pubs.sciepub.com/ajmcr/11/2/3/ajmcr-11-2-3.pdf Lyme disease Lyme carditis clinical diagnosis Pseudomonal pneumonia