A patient with a unique frameshift mutation in GPC3, causing Simpson-Golabi-Behmel syndrome, presenting with craniosynostosis, penoscrotal hypospadias, and a large prostatic utricle

Novel GPC3 Gene Mutation in Simpson-Golabi-Behmel Syndrome with Endocrine Anomalies: A Case Report

Simpson-Golabi-Behmel syndrome (SGBS) represents a rare X-linked recessive syndrome with prenatal and postnatal overgrowth, coarse facial features, congenital malformations, organomegaly and an increased risk of tumors. Mutations on the GPC3 gene, encoding the glypican-3 protein, have previously been shown to cause the disease. In this report, a 12-year-old Chinese boy was hospitalized in our institution for some clinical features of SGBS. His serum endocrine evaluation showed hormone level abnormalities, including high prolactin, high testosterone, high thyroid-stimulating hormone (TSH) levels, and low estradiol levels. Whole exome sequencing (WES) was performed in the patient for mutation analysis and a novel hemizygous mutation, c.185delT, p.(Leu62Cysfs*22), on the GPC3 gene, was identified. The mother was a heterozygous carrier. The SGBS patients might present with endocrine anomalies, which adds to the clinical heterogeneity of the disease. The novel GPC3 mutation c.185delT expands the mutational spectrum of the GPC3 gene.

The influence of genetics in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a common birth defect that is associated with significant morbidity and mortality, especially when associated with additional congenital anomalies. Both environmental and genetic factors are thought to contribute to CDH. The genetic contributions to CDH are highly heterogeneous and incompletely defined. No one genetic cause accounts for more than 1-2% of CDH cases. In this review, we summarize the known genetic causes of CDH from chromosomal anomalies to individual genes. Both de novo and inherited variants contribute to CDH. Genes causing CDH are increasingly identified from animal models and from genomic strategies including exome and genome sequencing in humans. CDH genes are often transcription factors, genes involved in cell migration or the components of extracellular matrix. We provide clinical genetic testing strategies in the clinical evaluation that can identify a genetic cause in up to ∼30% of patients with non-isolated CDH and can be useful to refine prognosis, identify associated medical and neurodevelopmental issues to address, and inform family planning options.

Simpson-Golabi-Behmel syndrome type 1 with subclinical hypothyroidism: A case report

RATIONALE

Simpson-Golabi-Behmel syndrome type 1 (SGBS1) is caused by mutations in GPC3 or in both GPC3 and GPC4. Physical manifestations of SGBS1 include fetal overgrowth and macrostomia, macroglossia. Subclinical hypothyroidism has never been reported in SGBS1 cases.

PATIENT CONCERNS

An 8-days-old boy was referred to our hospital with persistent hypoglycemia and special facies. And the infant showed elevated levels of thyroid-stimulating hormone (TSH). Free T4 and free T3 were normal.

DIAGNOSES

Definitive diagnosis of SGBS1 depends on clinical features and genetic testing. A nonsense mutation (c.1515C > A, p. Cys505*) was tested by whole-exome sequencing.

INTERVENTIONS

Normal blood glucose levels were maintained with glucose infusions. Levothyroxine was given to the patient for treating subclinical hypothyroidism.

OUTCOMES

The parents decided to abandon the treatment of the patient. We learned that the patient died of a lung infection by a telephone follow-up.

LESSONS

Subclinical hypothyroidism could be added to the known clinical manifestations of SGBS1.

Mutation update for the GPC3 gene involved in Simpson-Golabi-Behmel syndrome and review of the literature

Simpson-Golabi-Behmel syndrome (SGBS) is an X-linked multiple congenital anomalies and overgrowth syndrome caused by a defect in the glypican-3 gene (GPC3). Until now, GPC3 mutations have been reported in isolated cases or small series and the global genotypic spectrum of these mutations has never been delineated. In this study, we review the 57 previously described GPC3 mutations and significantly expand this mutational spectrum with the description of 29 novel mutations. Compiling our data and those of the literature, we provide an overview of 86 distinct GPC3 mutations identified in 120 unrelated families, ranging from single nucleotide variations to complex genomic rearrangements and dispersed throughout the entire coding region of GPC3. The vast majority of them are deletions or truncating mutations (frameshift, nonsense mutations) predicted to result in a loss-of-function. Missense mutations are rare and the two which were functionally characterized, impaired GPC3 function by preventing GPC3 cleavage and cell surface addressing respectively. This report by describing for the first time the wide mutational spectrum of GPC3 could help clinicians and geneticists in interpreting GPC3 variants identified incidentally by high-throughput sequencing technologies and also reinforces the need for functional validation of non-truncating mutations (missense, in frame mutations, duplications).

Simpson-Golabi-Behmel syndrome types I and II

Simpson-Golabi-Behmel syndrome (SGBS) is a rare overgrowth syndrome clinically characterized by multiple congenital abnormalities, pre/postnatal overgrowth, distinctive craniofacial features, macrocephaly, and organomegaly. Abnormalities of the skeletal system, heart, central nervous system, kidney, and gastrointestinal tract may also be observed. Intellectual disability, early motor milestones and speech delay are sometimes present; however, there are a considerable number of individuals with normal intelligence.

Genomic rearrangements and point mutations involving the glypican-3 gene (GPC3) at Xq26 have been shown to be associated with SGBS. Occasionally, these rearrangements also include the glypican-4 gene (GPC4). Glypicans are heparan sulfate proteoglycans which have a role in the control of cell growth and cell division.

Although a lethal and infrequent form (also known as SGBS type II) has been described, only the classical form of SGBS is reviewed in this work, whereas only some specific features on SGBS type II are commented.

We review all clinical and molecular aspects of this rare disorder, updating many topics and suggest a follow-up scheme for geneticists and primary care clinicians.

Closing the Gap: Genetic and Genomic Continuum from Syndromic to Nonsyndromic Craniosynostoses

Craniosynostosis, a condition that includes the premature fusion of one or multiple cranial sutures, is a relatively common birth defect in humans and the second most common craniofacial anomaly after orofacial clefts. There is a significant clinical variation among different sutural synostoses as well as significant variation within any given single-suture synostosis. Craniosynostosis can be isolated (i.e., nonsyndromic) or occurs as part of a genetic syndrome (e.g., Crouzon, Pfeiffer, Apert, Muenke, and Saethre-Chotzen syndromes). Approximately 85 % of all cases of craniosynostosis are nonsyndromic. Several recent genomic discoveries are elucidating the genetic basis for nonsyndromic cases and implicate the newly identified genes in signaling pathways previously found in syndromic craniosynostosis. Published epidemiologic and phenotypic studies clearly demonstrate that nonsyndromic craniosynostosis is a complex and heterogeneous condition supporting a strong genetic component accompanied by environmental factors that contribute to the pathogenetic network of this birth defect. Large population, rather than single-clinic or hospital-based studies is required with phenotypically homogeneous subsets of patients to further understand the complex genetic, maternal, environmental, and stochastic factors contributing to nonsyndromic craniosynostosis. Learning about these variables is a key in formulating the basis of multidisciplinary and lifelong care for patients with these conditions.