Schinzel-Giedion syndrome (SGS) is an ectodermal dysplasia syndrome chiefly characterized by a distinctive facial dysmorphosis, hydronephrosis, severe developmental delay, typical skeletal malformations, and genital and cardiac anomalies.
The incidence of SGS is not know. More than 50 cases have been reported worldwide to date.
At birth, SGS is quite easily characterized by the distinctive facial dysmorphism with a prominent forehead, midface retraction resembling a broadened ''figure-of-eight'' in marked cases and a short upturned nose, visceral abnormalities and hypertrichosis. Hydronephrosis is present in nearly all affected cases (91%). Cardiac abnormalities, including septal defects, valvular dysplasias, hypoplastic ventricles and patent ductus arteriosus are common (43%), as are other genitor-urinary abnormalities (76%), involving cryptorchidism, micropenis, hypospadias, hypoplastic uterus, labia minora and majora, deep labial sulcus, anteriorly displaced anus. Neonates frequently present with short limbs and limb malformations valgus or varus foot deformity, mesomelic brachymelia with hypoplastic and hyperconvex nails and single palmar creases of the hands. Affected neonates suffer from hypotonia and typically present with respiratory failure, all have a severe developmental delay accompanied by, often refractory, seizures, visual and hearing impairment. Additionally, a higher-than-normal prevalence for neuroepithelial tumors (17%) has been reported.
SGS is caused by de novo mutations in the SETBP1 gene, probably resulting in a gain-of-function or dominant-negative effect.
Diagnostic methods are based on clinical findings with the distinctive facial dysmorphism, hydronephrosis on the ultrasound, radiographic findings of multiple typical skeletal malformations including sclerotic skull base, wide occipital synchondrosis, increased cortical thickness/density and broad ribs. Under 12 months of age, skull radiographs reveal a gap between the 2 parts of the occipital bone and dense pyramids are also common. Genetic testing for SETBP1 is possible.
Other conditions with the distinctive midface retraction that could be considered differential diagnosis include fetal hydantoin or warfarin syndrome, zellweger syndrome, mucopolysaccharidosis, gangliosidosis , rhizomelic chondrodysplasia punctata (see these terms) as well as hypothyroidism
Hydrophrenosis is detactable on the prenatal ultrasound between 18-37 weeks of age, in about 40% of affected cases. Genetic testing is possible.
SGS is an autosomal dominant disorder. Practically all cases occur sporadically, identification of the proband should be undertaken along with genetic counseling for parents.
Management and treatment is supportive and consists of palliative care. The chief complications are respiratory failure, feeding intolerance, refractory seizures and frequent and recurrent infections such as pneumonia.
Prognosis is grave, with most affected patients not surving infancy, due to the progressive neurodegeneration, increased risk of tumors, recurrent infections and respiratory failure, although survival until adolescence has been reported.
Last update: April 2014