[Diagnosis of a child with Say-Barber-Biesecker-Young-Simpson syndrome due to variant of KAT6B gene].

Objective: To analyze the genotype and clinical phenotype of a 3-month-old female infant featuring unresponsiveness.

Methods: The infant was subjected to genetic testing, and her clinical features were compared with syndromes associated with variants of the candidate gene.

Results: The patient has featured long fingers, long and overlapped toes, musk-like face, blepharophimosis, ptosis, and lacrimal duct anomaly. She was found to harbor a heterozygous de novo variant NM_012330.3: c.3040C>T (p.Gln1014*) in exon 16 of the KAT6B gene. Her clinical phenotype and genotype have both conformed to Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS).

Conclusion: The child was diagnosed with SBBYSS syndrome due to the c.3040C>T (p.Gln1014*) variant of the the KAT6B gene. Discovery of the unique features has expanded the phenotypic spectrum of this syndrome.