would indicate Tietze syndrome. Additionally, symptoms such as tachycardia, hypotension, radiating pain, shortness of breath, fever, nausea, or a productive cough are unrelated to costochondritis. These signs warrant further investigation for other, more serious causes of chest pain. Cause The exact etiology of costochondritis is unknown. Repetitive minor trauma is proposed to be a likely cause, with risk factors such as strenuous coughing, exercise, and lifting identified. Infection of the costosternal joint may cause costochondritis in rare cases. Most cases of infectious costochondritis are caused by Actinomyces, Staphylococcus aureus, Candida albicans, and Salmonella. In rare cases, Escherichia coli can be a cause of infectious costochondritis. Pathogenesis The pathogenesis underlying the development of costochondritis remains unclear. Proposed mechanisms of pain include neurogenic inflammation, muscular imbalances, neuropathy of the intercostal nerves, myofascial pain, or mechanical dysfunction. Diagnosis Costochondritis is predominately a clinical diagnosis only after life-threatening conditions have been ruled out, with physical examination and medical history being considered. Before a costochondritis diagnosis is made, other serious causes of chest pain are investigated. Further evaluation for cardiopulmonary or neoplastic causes is typically based on history, age, and risk factors, with diagnostic imaging and tests, completed to assess for life-threatening emergencies. If there is a suspicion of infection or a rheumatoid condition, laboratory work may be conducted. A physical exam will assess for tenderness or pain upon palpation, with an absence of heat, erythema, or swelling. The physical exam may assess if the pain is worsened with movements of the upper body or breathing, and may be reproduced upon using the crowing rooster maneuver, the hooking maneuver, or the horizontal flexion maneuver. Medical history is considered in diagnosing costochondritis, such as inquiry regarding any recent trauma, coughing, exercise, or activity involving the upper body that may have caused the symptoms. Differential diagnosis Cardiopulmonary Life-threatening medical emergencies that may be associated with chest wall pain include acute coronary syndrome, aortic dissection, pneumothorax, or pulmonary embolism. Other cardiopulmonary causes of chest pain similar to that produced by costochondritis may include but are not limited to myocardial infarction, angina, and pericarditis. With costochondritis, the pain is typically worse with respiration, with movement, or within certain positions. Typically with other causes of chest pain, individuals will likely have radiating pain, shortness of breath, fever, a productive cough, nausea, dizziness, tachycardia, or hypotension. These conditions will be ruled out using tests such as X-rays, which will help assess