[Clinical phenotype and genetic analysis of a child with Acid-labile subunit deficiency due to variant of IGFALS gene].

OBJECTIVE

To explore the clinical phenotypes and genetic characteristics of a child with Acid-labile subunit deficiency (ALS).

METHODS

A male child diagnosed with ALS at Dongguan Maternal and Child Health Care Hospital in March 2021 was selected as the study subject. Clinical data of his family was collected. Peripheral blood samples were collected from the child and his parents. Following extraction of genomic DNA, whole-exome sequencing (WES) was carried out, and Sanger sequencing was used for family verification of candidate variants. Based on guidelines from the American College of Medical Genetics and Genomics (ACMG), the pathogenicity of the candidate variant was classified. This study was approved by the Medical Ethics Committee of the hospital (Ethics No.: 2020-6).

RESULTS

The patient, a 5-year-and-7-month-old boy, presented with short stature and delayed bone age. Endocrine examinations showed decreased serum concentrations of insulin-like growth factor-1 (IGF-1) and IGF binding protein-3 (IGFBP3). WES revealed that he has harbored compound heterozygous variants of the IGFALS gene, namely c.741_742del, p.Y248Pfs83 and c.272del, p.P91Rfs31. Sanger sequencing verified that the variants were inherited from his father and mother, respectively. According to the ACMG guidelines, c.741_742del, p.Y248Pfs83 and c.272del, p.P91Rfs31 variants were classified as likely pathogenic (PVS1+PM2_supporting). Based on the pre-set literature search strategy, 11 research literature on ALS were retrieved, which involved a total of 33 families and 62 patients. Combined with the patient in this study, 31 IGFALS gene variants were identified among the 63 patients, which mainly consisted of missense variants (20 types), with variant sites concentrated in exon 2. The main clinical features were short stature in conjunct with delayed puberty, with a significant genotype-phenotype correlation.

CONCLUSION

The IGFALS gene variants NM_004970.2: c.741_742del, p.Y248Pfs83 and c.272del, p.P91Rfs31 may be the genetic etiology in this family. This study has expanded the variant spectrum of the IGFALS gene and provided valuable information for the diagnosis, genetic counseling and clinical treatment of the disease.