[Clinical characteristics analysis of children with Noonan-like syndrome with loose anagen hair].

<b>Objective:</b> To analyze the clinical and genetic characteristics of children diagnosed with Noonan-syndrome associated with loose anagen hair(NS-LAH). <b>Methods:</b> A retrospective analysis was conducted on the clinical data of 5 children diagnosed with NS-LAH by the Endocrinology Department of the Capital Institute of Pediatrics from January 2018 to June 2024. This analysis encompassed the patients' demographic information, clinical manifestations, distinguishing features, treatment regimens, and prognostic outcomes to elucidate their clinical characteristics. Additionally, whole-exome sequencing and sanger sequencing were utilized to investigate the genetic etiology within the families, and the identified variations were interpreted according to the guidelines of the American College of Medical Genetics and Genomics. <b>Results:</b> Among the 5 NS-LAH patients, there were 3 boys and 2 girls, with ages at diagnosis ranging from 2.3 to 7.7 years old. All patients presented with short stature as a primary complaint. Birth histories were generally unremarkable, though case 2 and 5 of macrosomia were noted. In addition to the characteristic facial features of Noonan syndrome, short stature, and varying degrees of intellectual and motor developmental delay, all 5 patients exhibited sparse hair that was easily shed, as well as enlarged head circumferences. Four patients showed structural cardiac abnormalities, which included a case of hypertrophic cardiomyopathy, 2 cases of atrial septal defect, and 1 case of patent foramen ovale. Genetic analysis revealed heterozygous missense mutations in SHOC2 gene in 4 patients, comprising 3 cases with c.4A>G (p.S2G) and one case with c.519G>C(p.M173I). Additionally, one patient was found to have a heterozygous missense mutation c.146C>G(p.P49R) in PPP1CB gene. Three children were diagnosed with growth hormone deficiency and treated with growth hormone for 1.7, 2.7 and 0.5 years. This resulted in significant improvements in height, with annual incerases of 11.8, 8.4 and 13.0 cm, respectnely. Among the 4 patients with SHOC2 mutations, 2 developed systemic lupus erythematosus and 1 exhibited symptoms of arthritis. <b>Conclusions:</b> Growth failure is the primary complaint in patients with NS-LAH. Key characteristic findings include enlarged head circumference and sparse, loose hair. Growth hormone deficiency is commonly associated with NS-LAH, and growth hormone therapy is generally effective. Furthermore, patients carrying the classic mutation in SHOC2 (c.4A>G) may have an increased risk of developing autoimmune diseases.