A 13-month-old boy is brought to the emergency department due to cough and increased work of breathing. The patient's parents immigrated to the United States when he was 6 months old. He has a history of recurrent otitis media, pneumonia, and thrush as well as chronic diarrhea and failure to thrive. On physical examination, he is tachypneic and has perioral cyanosis. A chest radiograph shows bilateral interstitial opacities. The patient is admitted to the hospital and undergoes bronchoscopy. Analysis of the bronchoalveolar lavage fluid reveals Pneumocystis jirovecii. Which of the following is the most likely underlying diagnosis?

Question

A 13-month-old boy is brought to the emergency department due to cough and increased work of breathing.  The patient's parents immigrated to the United States when he was 6 months old.  He has a history of recurrent otitis media, pneumonia, and thrush as well as chronic diarrhea and failure to thrive.  On physical examination, he is tachypneic and has perioral cyanosis.  A chest radiograph shows bilateral interstitial opacities.  The patient is admitted to the hospital and undergoes bronchoscopy.  Analysis of the bronchoalveolar lavage fluid reveals Pneumocystis jirovecii. Which of the following is the most likely underlying diagnosis?

Quizplus · Accepted Answer

Eductional Objective: Severe combined immunodeficiency is caused by a genetic defect in T cell development, leading to loss of both cellular and humoral immunity.  Patients present in infancy with recurrent bacterial, viral, fungal, and opportunistic infections as well as failure to thrive and chronic diarrhea.

A 13-Month-Old Boy Is Brought to the Emergency Department Due