No abstract

Cystic fibrosis (CF), a monogenic disease, is the most common life-shortening autosomal recessive disease that afflicts people of Northern European descent. It was first formally reported to the worldwide medical community in 1949. According to the American Cystic Fibrosis Foundation patient registry, there are currently more than 30 000 CF patients in the United States and more than 70 000 CF patients throughout the world. Globally, about 1000 cases of CF are newly diagnosed every year, with over 75% of CF patients diagnosed at 2 years of age and an average age at diagnosis of about 3 years of age. CF incidence rates vary around the world, but rates as high as 1 in 2000 to 3000 live births are associated with Caucasian populations with Northern European ancestry. The median predicted survival time of CF patients in the United States is approximately 47.4 years (95% CI, 44.2-50.3) according to the Cystic Fibrosis Foundation 2018 Registry Report. However, epidemiological data on CF prevalence in China have not yet been reported, aside from observations that the genotypic spectrum of Chinese CF varies widely among resident subpopulations based on their geographical and ethnic origins.Numerous animal CF models have been established based on specific types of human CFTR mutations, but models differ in their effectiveness in mirroring features of human CF-specific disease.For example, the mouse CF model differs markedly from human CF at the pathological level, while at the molecular level CFTR genes of pig and human are highly homologous, but their corresponding CFTR protein structures and functions are vastly different. At present, ferret and rabbit CF models hold promise as human CF models, but additional models based on other species should also be evaluated.Meanwhile, the introduction of human CFTR genes harboring CFTR mutations into genomes of animals holds promise as a strategy for creating better animal models for human CF. Nevertheless, current animal models each have their own unique features that are useful for studying particular aspects of human CF disease, as described below.

Hereditary hemorrhagic telangiectasia (HHT) can be clinically diagnosed, but children often lack characteristic features. We report a family with homozygous growth differentiation factor 2 (GDF2)–related HHT diagnosed by genetic testing. A boy aged 5 years and 2 months presented with isolated hypoxemia. He was the product of a consanguineous marriage; his parents were second cousins. Physical examination revealed cyanosis of nail beds and clubbed fingers. Pulse oxygen saturation was 84% to 89%. Lung function, contrast-enhanced lung computed tomography, and noncontrast echocardiography were normal. A pulmonary perfusion scan revealed radioactivity in the brain and bilateral kidney, suggesting the existence of a intrapulmonary shunt. Whole-exome sequencing revealed a homozygous variant [c.1060_1062delinsAG (p.Tyr354ArgfsTer15)] in GDF2, which was found to be inherited from his heterozygous parents. At the age of 8 years, he developed epistaxis, and an angiogram revealed diffuse pulmonary arteriovenous malformations. At the age of 9 years, he was treated with sirolimus, and his condition improved significantly. However, his now 7-year-old sister with the same homozygous variant currently has no symptoms. Physical examinations revealed 1 pinpoint-sized telangiectasia on the chest of his mother and a vascular lesion on the forehead of his sister. Additionally, the patient’s father and great-uncle had a history of mild to moderate epistaxis. Mutation in GDF2 is a rare cause of HHT. Ours is the first report of homozygous GDF2-related HHT; in addition, this variant has not been reported previously. In our report, we also confirm variable expressivity, even with the same pathogenic variant in GDF2-related HHT.