title: C1
design: Background: Congenital ectopia lentis is characterized by dislocation of the lens caused by partial or complete abnormalities in the zonular fibers. It can be caused by either systemic diseases or isolated ocular diseases. Gene detection techniques can provide valuable information when an etiological diagnosis is challenging. Herein, we report the case of a six-year-old girl with a confirmed diagnosis of isolated ectopia lentis caused by a compound heterozygous ADAMTSL4 gene mutation.Case Presentation and Methods: The patient was a six-year-old girl with strabismus in the right eye. Slit lamp examination revealed that the lens in the right eye was opacified and dislocated, without an ectopic pupil. She consented to a physical examination (placing particular emphasis on the skeletal system), and the results were unremarkable. A detailed ocular examination exposed that the axial length was 21.39 mm (OD) and 22.20 mm (OS) as measured by IOL Master, and 21.78 mm (OD) and 22.38 mm (OS) as assessed by ultrasound; B ultrasonography and macular optical coherence tomography were normal. Echocardiography determined that the internal diameter of the aortic root was 20 mm, while its Z score was 2. After getting a detailed medical history from her parents, we learned that her prenatal and developmental status were normal. Her family members, including her elder sisters and little brother, were never diagnosed with ocular abnormalities during childhood; hence she was the proband of ectopia lentis in her family. Gene detection demonstrated the presence of a compound heterozygous mutation in the ADAMTSL4 gene [C. 2270dupG (P.gly758TRpFS *59) and C. 2110A>G (P.Ser704Gly)], and the diagnosis of isolated ectopia lentis was confirmed. She underwent lens extraction, and a sutured scleral-fixated posterior chamber IOL was placed in the right eye. The best-corrected visual acuity was 0.1 one month postoperatively. Conclusion: In this study, a diagnosis of isolated ectopia lentis was made through whole exons sequencing, and the variant C. 2110A>G (P.Ser704Gly) was discovered, which may be associated with the development of ectopia lentis and early-onset cataract in this patient.