A newborn with a pathogenic variant in ASXL2 expanding the phenotype of SHAPNS: a case report and literature review

BACKGROUND: Shashi-Pena syndrome (SHAPNS) is a developmental disorder caused by mutations in additional sex combs-like Protein 2 (ASXL2). Since 2016, only 12 cases from 10 families have been reported. However, neonatal period characteristics remain largely unknown. Herein, we report a case with a pathogenic variant in ASXL2 in a newborn. CASE DESCRIPTION: A newborn was diagnosed with a previously unreported de novo truncating mutation in ASXL2 (NM_018263.6) at 21 days and the clinical characteristics of all probands with ASXL2-related SHAPNS was reported in the literature. He had persistent hypoglycemia caused by inappropriate insulin levels and achieved stable glucose levels after octreotide treatment. Magnetic resonance imaging (MRI) revealed a small cerebellum, and fundoscopy showed bilateral retinal paving-stone-like white lesions. The results of trio-based whole exome sequencing (WES) were returned on the 21st day of life, and a heterozygous de novo truncating pathogenic c.1792C>T (p.Gln598*) variant in exon 11 of the ASXL2 gene was identified. The clinical features of our patient and another 10 probands with ASXL2-related SHAPNS reported in the literature were included in this review. More than half shared recognizable clinical features, including hypertelorism (11/11), broad nasal tip (10/11), arched eyebrows (9/11), a large V-shaped glabellar nevus flammeus on the forehead (9/11), low-set ears (8/11), posteriorly rotated ears (7/11), proptosis (6/11) and deep palm creases (6/11). Major clinical issues included feeding difficulties (10/11), developmental delay (10/11), skeletal and/or extremity abnormalities (8/11), progressive macrocephaly (8/11), hypotonia (8/11), hypoglycemia (6/11) and seizures (6/11). Neurodevelopmental regression was possible in patients (2/11) with normal MRI findings who later developed nonfebrile seizures. CONCLUSIONS: We present a newborn diagnosing the SHAPNS by trio-WES, which is the earliest age of diagnosis. The application of octreotide for hypoglycemia, the small cerebellum and bilateral paving-stone-like white lesions of the retinas are described for the first time in an individual with ASXL2-related SHAPNS. Additional clinical reports of neonates with damaging ASXL2 variants are necessary to verify the mechanism and optimal treatment of ASXL2-related hypoglycemia, neurological damage and optic impairment. Neurological, endocrinological, ophthalmological, and rehabilitative follow-ups of these patients are necessary and important.