Antibiotics are not helpful for many lower respiratory tract infections caused by viruses. Acute bronchitis usually does not require antibiotic treatment. Antibiotics for lower respiratory tract infections are mainly used for patients with acute exacerbations of chronic bronchitis or pneumonia. Accordingly, the indication for treatment of bacterial lower respiratory tract infections is selected by considering the patient's age, the severity of the disease, and the presence of underlying disease.

Mixed connective tissue disease is an autoimmune disease that mostly affects young women. It causes a range of symptoms similar to other autoimmune diseases. Symptoms tend to progress gradually, making early detection difficult.