Cystic fibrosis caused by homozygous gene mutation leading to pulmonary involvement: a case report.

Cystic fibrosis (CF) is an autosomal recessive monogenic disorder caused by mutations in the CF transmembrane conductance regulator () gene, resulting in impaired protein function. Predominantly affecting Caucasians, CF involves multiple organ systems, including the lungs, pancreas, liver, gastrointestinal tract, and reproductive system. In contrast, CF remains rare among Asian populations, particularly within the Chinese demographic. Reported cases in China predominantly feature heterozygous mutations, with no confirmed instances of homozygous mutations. A 15-year-old male presented with a 6-year history of recurrent cough and purulent yellow-green sputum production, without hemoptysis. Whole exome sequencing identified a homozygous mutation, NM_000492.4:c.2290C>T (p.Arg764*), confirming the diagnosis of CF complicated by pulmonary infection. The patient received intravenous cefoperazone/sulbactam (2.25 g every 12 hours) and moxifloxacin (400 mg once daily). Symptomatic improvement was achieved after 2 weeks, and azithromycin was prescribed (three times weekly) upon discharge. This case highlights the importance of considering gene mutations in patients with prolonged respiratory symptoms (recurrent cough and sputum production) and imaging findings indicative of pulmonary CF. Whole exome sequencing is recommended to determine the genetic etiology in such cases and guide targeted management.