Growth hormone treatment in Aarskog syndrome: analysis of the KIGS (Pharmacia International Growth Database) data

FGD1-related Aarskog-Scott syndrome: Identification of four novel variations and a literature review of clinical and molecular aspects

Patients with Aarskog-Scott syndrome (AAS) have short stature, facial anomalies, skeletal deformities, and genitourinary malformations. FYVE, RhoGEF, and PH domain-containing 1 (FGD1) is the only known causative gene of AAS. However, the diagnosis of AAS remains difficult, and specific treatments are still absent. Patients suspected with AAS were recruited, and clinical information was collected. Genetic testing and functional analysis were carried out for the diagnosis. By literature review, we summarized the clinical and genetic characteristics of FGD1-related AAS and analyzed the genotype-phenotype correlation. Five patients were recruited, and four novel FGD1 variants were identified. The diagnosis of AAS was confirmed by genetic analysis and functional study. Three patients treated with growth hormone showed improved heights during the follow-up period. By literature review, clinical features of AAS patients with FGD1 variants were summarized. Regarding FGD1 variations, substitutions were the most common form, and among them, missense variants were the most frequent. Moreover, we found patients with drastic variants showed higher incidences of foot and genitourinary malformations. Missense variants in DH domain were related to a lower incidence of cryptorchidism.   Conclusion: We reported four novel pathogenic FGD1 variations in AAS patients and confirmed the efficacy and safety of growth hormone treatment in FGD1-related AAS patients with growth hormone deficiency. Additionally, our literature review suggested the crucial role of DH domain in FGD1 function. What is Known: • Aarskog-Scott syndrome is a rare genetic disease, and the only known cause is the variant in FGD1 gene. The typical clinical manifestations of AAS include facial, skeletal, and urogenital deformities and short stature. What is New: • We reported four novel FGD1 variants and reported the treatment of growth hormone in FGD1-related AAS patients. Our genotype-phenotype correlation analysis suggested the crucial role of DH domain in FGD1 function.

Case Report: Aarskog-scott syndrome caused by FGD1 gene variation: A family study

Aarskog-Scott syndrome is a rare genetic disorder characterized by short stature, abnormal facial features, and digital and genital deformities. FGD1 gene variation is the known cause of this disorder. This paper described a Chinese family study of Aarskog-Scott syndrome in which the main patients were two brothers. Then, the relationship between genotype and phenotype in Aarskog-Scott syndrome was investigated preliminarily. A new FGD1 gene variant was revealed in this study, providing insights into the link between phenotype and genotype variations in Aarskog-Scott syndrome as well as a foundation for its diagnosis and treatment.

FGD1 Variant Associated With Aarskog-Scott Syndrome

BACKGROUND

Aarskog-Scott syndrome, a rare X-linked genetic disorder, is identified by combined clinical manifestations of short stature, facial, skeletal, and genital anomalies. Annually, two or three new cases are diagnosed with Aarskog-Scott syndrome, which is associated with FGD1 variants. However, there is no specific treatment for Aarskog-Scott syndrome due to its unclear mechanism.

METHODS

Clinical data were collected when the patient first visited the hospital. Trio whole-exome sequencing and Sanger sequencing were performed for the genetic cause of disease. To evaluate the pathogenicity of the variants in vitro, stable cell lines were constructed using lentivirus infection in 143B cell. Furthermore, Western blot was used to verify the expression of signaling pathway-related proteins, and the transcription levels of osteogenic-related genes were verified by luciferase reporter gene assay.

RESULTS

A 7-year-old boy was manifested with facial abnormalities, intellectual disability, and short stature (-3.98 SDS) while the growth hormone level of stimulation test was normal. Trio whole-exome sequencing and Sanger sequencing identified a variant (c.1270A>G, p.Asn424Asp) in FGD1 gene. The Asn424 residue was highly conserved and the hydrogen bond in the FGD1 variant protein has changed, which led to decrease in the interaction with CDC42 protein. In vitro study showed that the Asn424Asp variant significantly decreased the transcription levels of OCN, COL1A1, and ALP activity, and it activated the phosphorylation of JNK1.

CONCLUSION

Molecular biological mechanisms between abnormal expression of FGD1and Aarskog-Scott syndrome remain poorly understood. In our study, c.1270A>G variant of FGD1 resulted in Aarskog-Scott syndrome, and the analysis of pathogenicity supports the deleterious effect of the variant. Furthermore, we demonstrated the weakened affinity of the mutant FGD1 and CDC42. Decreased expression of osteogenic-related gene and abnormal activation of JNK1 were also shown in this work.

A novel frameshift mutation in the FGD1 gene causing Aarskog-Scott syndrome patient with hypogonadism: a case report

Aarskog-Scott syndrome (AAS) is most commonly inherited as an X-linked recessive genetic disease caused by FGD1 mutations. AAS patients are most frequently male, and the clinical manifestations of facial abnormalities, skeletal deformities, and abnormal genitalia comprise a characteristic triad of diagnostic features. The results on the clinical and molecular analysis of a family that reveals a novel FGD1 gene frameshift mutation in an 11-year-old boy displaying bilateral cryptorchidism associated with hypogonadism are reported here. This patient exhibited a characteristic triad of diagnostic features of ASS, including short stature, facial abnormalities, joint laxity, and typical scrotal fold. Whole-exome sequencing revealed the novel hemizygous mutation c.500delA in exon 3 of the patient's FGD1 gene, resulting after a frameshift in the Tyr167 residue, while his mother is heterozygous of the same variant. Further in silico studies were performed to identify the pathological consequence of this gene mutation. Thus, our study shows that frameshifts disrupting the RhoGEF gene domain of FGD1 represent the most prevalent causal mutations underlying AAS and expand the phenotypic and mutational spectra of this disease. Improved understanding of the phenotypic and pathological heterogeneity accompanying FGD1 mutation can greatly enhance the clinical prognostic capabilities in the future and aid genetic counseling for AAS patients.

Syndromic disorders with short stature

Short stature is one of the major components of many dysmorphic syndromes. Growth failure may be due to a wide variety of mechanisms, either related to the growth hormone (GH)/insulin-like growth factor axis or to underlying unknown pathologies. In this review, the relatively more frequently seen syndromes with short stature (Noonan syndrome, Prader-Willi syndrome, Silver-Russell syndrome and Aarskog-Scott syndrome) were discussed. These disorders are associated with a number of endocrinopathies, as well as with developmental, systemic and behavioral issues. At present, GH therapy is used in most syndromic disorders, although long-term studies evaluating this treatment are insufficient and some controversies exist with regard to GH dose, optimal age to begin therapy and adverse effects. Before starting GH treatment, patients with syndromic disorders should be evaluated extensively.

Advances in Growth Hormone Therapy: A New Registry Tool

Growth hormone (GH) deficiency is a rare condition, and physicians may lack clinical experience of its treatment. Despite evidence for the efficacy and tolerability of GH therapy, a substantial proportion of patients remain untreated. Registries and other large-scale databases are an important tool for expanding the evidence base for GH treatment. Since the mid-1980s, registries have provided data on important aspects of the safety and efficacy of GH treatment. Registries have also allowed pooling of data from patients with rare conditions that could otherwise not be recruited in sufficient numbers for clinical trials. Importantly for patients and their relatives, use of registry data has allowed the development of prediction models that indicate the likely outcomes of treatment. MEGHA (Metabolic Endocrinology and Growth Hormone Assessment) is a recently developed, observational database with a number of features not found in existing registries, including its use as a day-to-day clinical management tool, the ability to create individual sub-studies, direct comparison of personal data against the full database, and a particular focus on the transition from childhood to adulthood. This creative registry is a promising instrument for further research into GH-related disorders that will improve GH therapy and thus provide benefits for patients.