Isolated atrophy of the pectoralis major muscle (PMM) secondary to traumatic lesion of the medial pectoral nerve is a known entity in the field of neuromuscular electrodiagnostics. Recent literature has begun describing a Pectoral Gap Phenomenon in which this atrophy occurs bilaterally as an overuse injury, leading to a marked concavity in the central chest wall musculature. While there is limited information in science journals on this topic, social media posts on weight lifting discuss the topic frequently. We report a case in which a soldier's body armor crushed the lateral medial and pectoral nerves against the anterior chest wall causing permanent upper body weakness. To optimize military medical readiness, awareness of this disorder and the pathophysiology causing it should spread so as to mitigate this potential for significant disability.
Keywords: Steinert syndrome; bilateral pectoralis major atrophy; body armor; pectoral gap syndrome.