Differential Diagnosis for a 15-year-old boy with recurrent upper and lower respiratory tract infections and finger clubbing

• Single most likely diagnosis:
  • Cystic Fibrosis (CF): This condition is characterized by recurrent respiratory infections, malabsorption, and finger clubbing due to chronic hypoxia. CF is a common cause of recurrent respiratory infections in children and young adults, making it the most likely diagnosis given the symptoms.
• Other Likely diagnoses:
  • Bronchiectasis: A condition where the airways of the lungs become abnormally widened, leading to recurrent respiratory infections and potential finger clubbing. It can be primary or secondary to various conditions, including infections and immune deficiencies.
  • Primary Ciliary Dyskinesia (Kartagener Syndrome): Characterized by chronic respiratory infections, situs inversus, and infertility due to defective ciliary function. Finger clubbing can also occur.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.):
  • Immunodeficiency disorders: Conditions such as Severe Combined Immunodeficiency (SCID) or Common Variable Immunodeficiency (CVID) can present with recurrent infections. Early diagnosis is crucial for management and prevention of complications.
  • Tuberculosis: Although less common in this age group without specific risk factors, TB can cause chronic infections and should be considered, especially if there's a history of exposure or travel to endemic areas.
• Rare diagnoses:
  • Alpha-1 Antitrypsin Deficiency: A genetic disorder that can lead to lung disease, including chronic obstructive pulmonary disease (COPD) and liver disease. It's less common but should be considered in the differential for recurrent respiratory infections.
  • Yellow Nail Syndrome: A rare condition characterized by yellow discoloration of the nails, lymphedema, and recurrent respiratory infections. It's an uncommon cause of the symptoms described but fits the pattern of recurrent infections and potential for clubbing due to chronic illness.

Given the options provided (A. Ileitis, B. Pancreatitis), neither directly correlates with the primary symptoms of recurrent upper and lower respiratory tract infections and finger clubbing. However, Cystic Fibrosis, the single most likely diagnosis, can cause pancreatitis due to the obstruction of the pancreatic ducts by thick secretions, leading to inflammation of the pancreas. Therefore, among the options provided, B. Pancreatitis is more closely associated with the likely underlying condition (Cystic Fibrosis) than A. Ileitis.