A 4-year-old girl is brought to your clinic by her parents for evaluation of persistent health issues. Her medical history reveals chronic cough and frequent respiratory infections, leading to multiple hospitalizations. She has had poor growth despite a good appetite and shows signs of malabsorption such as greasy stools. On physical examination, the child has clubbing of the fingers and appears underweight for her age. Family history reveals that a cousin has a metabolic disorder requiring dietary restrictions, and another relative was diagnosed with lung disease as a teenager. You suspect an inherited genetic condition and consider autosomal recessive disorders in your differential diagnosis. Which of the following is an autosomal recessive disorder?
