Clinical manifestations and genetic mutation analysis of patients with mucopolysaccharidosis type VII in China

Objective: This study aimed to explore the clinical and genetic features of Chinese patients with mucopolysaccharidosis type VII (MPS VII), thereby improving early detection, disease management, and patient outcomes. Methods: A retrospective review of medical records for five patients presenting with coarse facial features, rib protrusion, chest deformities, and scoliosis was conducted. Exome sequencing was employed to identify causative genetic mutations. Results: The study comprised five patients (four males, one female) with disease onset at six months of age (range: 0-1.5 years). Common symptoms included coarse facial features, skeletal abnormalities, delayed motor and language development, and intellectual disability. Approximately 80% of the patients exhibited multiple skeletal dysplasias, enlarged adenoids or tonsils, and snoring; 60% had hernias; 40% reported hearing loss and hepatosplenomegaly. Less frequent manifestations were short stature, valvular heart disease, non -immune hydrops fetalis, and corneal opacity. All patients demonstrated elevated urine glycosaminoglycans levels and absent 8-glucuronidase activity in leukocytes. Exome sequencing identified compound heterozygous mutations in the GUSB gene in all four tested patients, uncovering seven mutations in total, three of which were novel (c.189G > A, c.869C > T, and c.1745 T > C). Furthermore, prenatal diagnosis through chorionic villus sampling in subsequent pregnancies of one patient's mother revealed both fetuses had normal 8-glucuronidase activity and no disease -causing mutations in the GUSB gene. Conclusion: The study's patients all presented with classic symptoms of MPS VII due to 8-glucuronidase deficiency, with three new pathogenic mutations identified in the GUSB gene. Genetic counseling and prenatal testing were highlighted as crucial for disease prevention.