RESUMEN
OBJECTIVE: To analyze the clinical and genetic characteristics of a boy featuring unexplained developmental delay, malnutrition and distinct facial appearance. METHODS: Physical examination was carried out for the child. Peripheral blood samples were collected from the child and his parents for the extraction of genomic DNA and trio-whole exome sequencing. Candidate variants were verified by Sanger sequencing. RESULTS: The patient had facial dysmorphism including nasal alae aplasia, scalp defect and teeth deformities, in addition with recurrent diarrhea due to pancreatic exocrine insufficiency. DNA sequencing revealed that he has harbored compound heterozygous variants of the UBR1 gene, namely c.3167C>G (p.S1056X) and c.1911+14C>G, which were inherited from his father and mother, respectively. Database search has suggested the c.3167C>G to be a novel nonsense variant and c.1911+14C>G a known splicing variant. Based on the guidelines of the American College of Medical Genetics and Genomics, the two variants were predicted to be pathogenic and likely pathogenic, respectively. CONCLUSION: The child was diagnosed with Johanson-Blizzard syndrome due to the compound heterozygous variants of the UBR1 gene. Above finding has enriched the mutational spectrum of the UBR1 gene and provided a basis for genetic counseling for this family.