Males and females can present similarly with Simpson-Golabi-Behmel syndrome type 1 (SGBS1). However, there is skewing of males to females in a 9:1 ratio. Individuals of both sexes present with overgrowth, characteristic facial features, skeletal abnormalities, and genitourinary dysfunction. Males often present with cryptorchidism. Females are less likely to present with severe manifestations of SGBS1, potentially due to skewed X-chromosome inactivation. There have not been extensive studies of sex differences in SGBS1 due to the small number of females reported to date and mildly affected or unaffected female carriers who do not present until they have an affected son.
Affected Males
SGBS1 is characterized by pre- and postnatal overgrowth, distinctive facies, and variable visceral, skeletal, and neurodevelopmental abnormalities. To date, 159 individuals have been identified with a pathogenic variant in GPC3 [Klein et al, unpublished data]. The following description of the phenotypic features associated with this condition is based on these reports.
Table 2.
Simpson-Golabi-Behmel Syndrome Type 1: Frequency of Select Features
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System | Feature | % of Persons w/Feature |
---|
Overgrowth
| Overgrowth (linear growth ≥2 SD above mean for age & sex) | 85% |
Macrocephaly (OFC ≥2 SD above mean for age & sex) | 34% |
Facial features
| Characteristic facial features | 87% |
Macroglossia | 88% |
Macrostomia | 85% |
Ear deformities | 80% |
Frontal bossing | 85% |
High-arched or cleft palate | 75% |
Hypertelorism | 85% |
Thick lips | 63% |
Cardiac
| Congenital heart disease | 55% |
Conduction cardiac defects | 36% |
Genitourinary
| Renal dysplasia, nephromegaly, duplicated renal system | 72% |
Cryptorchidism, hypospadias in males | 61% |
Musculoskeletal
| Hand & foot anomalies (brachydactyly, cutaneous syndactyly, polydactyly) | 49% |
Neurodevelopmental
| Intellectual disability | 60% |
Neoplasia
| Hepatoblastoma & Wilms tumor (most common) | 11% |
Other features
| Supernumerary nipples | 64% |
Diastasis recti, umbilical hernia | 35% |
Diaphragmatic hernia | 29% |
Organomegaly | 59% |
Klein et al, unpublished data
OFC = occipital frontal circumference; SD = standard deviation
Overgrowth
Somatic overgrowth. Virtually all individuals with SGBS1 have either pre- or postnatal overgrowth. 68% of individuals present with postnatal overgrowth and 61% of individuals present with prenatal overgrowth [Klein et al, unpublished data]. At this time, no reference ranges or SGBS1-specific growth curves have been developed. There are currently no reports of hemihypertrophy or lateralized overgrowth.
As with other overgrowth syndromes, hypoglycemia may be present in the neonatal period; however, hypoglycemia is rare in SGBS1 and is not considered to be a cardinal feature.
Macrocephaly. Macrocephaly is reported in just over one third of individuals with SGBS1. Most present with macrocephaly in the prenatal period and continue to be macrocephalic throughout their life [Klein et al, unpublished data]. The most common complication of congenital macrocephaly in individuals with SGBS1 is difficulties with vaginal delivery, leading to increased risk of cesarean section deliveries [Klein et al, unpublished data]. Additionally, ventriculomegaly and ventricular hemorrhage, which are seen in some affected individuals, may confound the early identification of macrocephaly [
Garganta & Bodurtha 1992,
Li & McDonald 2009].
Characteristic facies include the following:
Widely spaced eyes, epicanthal folds, and downslanted palpebral fissures
Redundant, furrowed skin over the glabella
Wide nasal bridge and anteverted nares in infants; broad nose and coarsening of the facial features in older individuals
Prominent forehead
Macrostomia
Macroglossia with or without a midline groove in the lower lip and/or deep furrow in the middle of the tongue
Cleft lip and/or submucous cleft palate (with a bifid uvula); high and narrow palate
Micrognathia in neonates; large mandible (macrognathia) in older individuals
Cardiac. A range of cardiac features are seen:
Congenital heart defects are variable; septal defects are common. Pulmonic stenosis, aortic coarctation, transposition of the great vessels, and patent ductus arteriosus or patent foramen ovale have been reported.
Genitourinary. Nephromegaly, nephroblastomatosis, multicystic kidneys, hydronephrosis, hydroureter, supernumerary kidneys, and duplicated ureters have been described [Schmidt et al 2017, Reischer et al 2021].
Other genitourinary anomalies include hypospadias, penile hypoplasia, ambiguous genitalia, anal atresia, bifid scrotum, cryptorchidism, hydrocele, and inguinal hernia [Hughes-Benzie et al 1996, Romanelli et al 2007, Villarreal et al 2013, Halayem et al 2016, Magini et al 2016, Fu et al 2019].
Musculoskeletal. Skeletal anomalies can include vertebral fusion, scoliosis, pectus excavatum, rib anomalies (including cervical ribs), congenital hip dislocation [Terespolsky et al 1995, Garavelli et al 2012], small sciatic notches, and flared iliac wings [Chen et al 1993, Garavelli et al 2012]. Extra lumbar vertebrae, spina bifida (open and occulta) [Hughes-Benzie et al 1992, Van Borsel et al 2008], coccygeal skin tag, metaphyseal dysplasia of the femur [Yamashita et al 1995], and bony appendage have also been documented [Golabi & Rosen 1984].
Hand anomalies such as large hands, broad thumbs, and brachydactyly are common. Other findings include syndactyly, clinodactyly, and postaxial polydactyly. Striking index finger hypoplasia with congenital abnormalities of the proximal phalanx have been reported [Verloes et al 1995, Day & Fryer 2005]. Nail dysplasia, hypoplasia (particularly of the index finger), and hypoconvexity are common [Garavelli et al 2012, Cottereau et al 2013, Bu et al 2022].
Advanced bone age, including presence of ossified carpal bones in a newborn, has been described [Chen et al 1993, Watanabe et al 2022].
Neurologic and neurodevelopmental. Neurologic manifestations are perhaps the most variable findings. Hypotonia and absent primitive reflexes, a high-pitched cry in neonates, seizures, and abnormal EEG have all been described.
Normal intelligence has been described, but mild-to-severe intellectual disability is common, with language delay being the most characteristic finding.
Hydrocephalus, epilepsy, and attention-deficit/hyperactivity disorder may also be present [Van Borsel et al 2008, Tenorio et al 2014, Halayem et al 2016].
Brain abnormalities have been reported, including agenesis of the corpus callosum, Chiari malformation, hydrocephalus, and hypoplasia of the cerebellar vermis [Young et al 2006].
Neoplasia. The tumor risk in SGBS1 is estimated to be 11.3%, with the most common types being hepatoblastoma and Wilms tumor [Shimojima et al 2016, Spencer et al 2016]. The median age of neoplastic onset is 17.5 months with a 7:1 male-to-female ratio. With this risk and based on the guidelines for screening in cancer predisposition syndromes that lead to hepatoblastoma and Wilms tumor, individuals with SGBS1 should undergo tumor screening (see Surveillance).
Additionally, several tumors have been reported in single individuals, but it is unknown if they are related to the pathogenesis of SGBS1 or reflect the underlying population-level neoplastic risk. Each of the following has been reported in single individuals:
Other manifestations
Oropharynx. Macroglossia is a characteristic feature. In some cases, the tongue may enlarge such that it interferes with breathing and/or sleeping [
Paludetti et al 2003], but the need for surgical intervention has not been determined to date. Other anomalies include various degrees of palatal clefting (including submucous cleft and bifid uvula), laryngeal cleft, and laryngeal web. Obstructive sleep apnea may be present. Silent aspiration leading to chronic respiratory infections and bronchiectasis has also been described [
Glamuzina et al 2009,
Tenorio et al 2014].
Eyes. Esotropia, cataracts, and coloboma of the optic disc [
Golabi & Rosen 1984] have been noted. Ocular nerve palsies and strabismus can occur.
Neck. Cystic hygroma, thymic hypoplasia, and generalized lymphoid atrophy have been described but are rare [
Chen et al 1993].
Gastrointestinal. Gastrointestinal anomalies include pyloric ring, Meckel's diverticulum, intestinal malrotation [
Golabi & Rosen 1984], hepatosplenomegaly, pancreatic hyperplasia of islets of Langerhans, choledochal cysts [
Kim et al 1999,
Shimojima et al 2016], duplication of the pancreatic duct, polysplenia, liver cysts, biliary atresia [
Jedraszak et al 2014], inguinal hernia, and supernumerary kidney [
Schmidt et al 2017,
Chong et al 2018].
Heterozygous Females
Due to skewed X-chromosome inactivation, heterozygous females can have variable manifestations of SBGS1 ranging from completely unaffected to fully recapitulating the severe phenotype, including overgrowth, widely spaced eyes, broad and upturned nasal tip with prominent columella, macrostomia, prominent chin, hypoplastic fingernails, coccygeal skin tag and bony appendage, extra lumbar and thoracic vertebrae, and accessory nipples [Golabi & Rosen 1984, Fernandes et al 2021]. Tall stature, coarse facial features, and developmental delay have also been reported [Gertsch et al 2010].
To date, nine heterozygous females with clinical expression of SGBS1 have been reported [Punnett 1994, Pilia et al 1996, Yano et al 2011, Mujezinović et al 2016, Shimojima et al 2016, Vaisfeld et al 2017, Schirwani et al 2019]. These cases encompass the full spectrum of SGBS1. Further, cancer has been reported in some of these affected females, including two females with a heterozygous GPC3 pathogenic variant with two different types of cancer: one had a seropapilliferous cystoadenoma, a low-grade ovarian carcinoma; the other had breast cancer [Gurrieri et al 2011]. Information was insufficient to exclude other possible genetic causes for breast/ovarian cancer in the family. An affected female with a Wilms tumor has also been reported [Fernandes et al 2021], as well as a female with a hepatoblastoma [Shimojima et al 2016].