Clinical characteristics: Ritscher-Schinzel syndrome (RSS) is a clinically recognizable condition that includes the cardinal findings of craniofacial features, cerebellar defects, and cardiovascular malformations resulting in the alternate diagnostic name of 3C syndrome. Dysmorphic facial features may include brachycephaly, hypotonic face with protruding tongue, flat appearance of the face on profile view, short midface, widely spaced eyes, downslanted palpebral fissures, low-set ears with overfolding of the upper helix, smooth or short philtrum, and high or cleft palate. Affected individuals also typically have a characteristic metacarpal phalangeal profile showing a consistent wavy pattern on hand radiographs. RSS is associated with variable degrees of developmental delay and intellectual disability. Eye anomalies and hypercholesterolemia may be variably present.
Diagnosis/testing: The diagnosis of Ritscher-Schinzel syndrome is established in a proband with suggestive clinical findings, including characteristic dysmorphic facial features, and/or by the identification of biallelic pathogenic variants in WASHC5 in a male or female or a hemizygous pathogenic variant in CCDC22 in a male by molecular genetic testing.
Management: Treatment of manifestations: Standard treatment for obesity, obstructive sleep apnea, cleft palate, congenital heart defects, hypercholesterolemia, renal anomalies, immunodeficiency, and developmental delay / intellectual disability.
Surveillance: Measurement of growth parameters (particularly weight); assessment of developmental progress, mobility, self-help skills, and educational needs; and monitoring for symptoms of obstructive sleep apnea at each visit; ophthalmology evaluation annually or as clinically indicated; measurement of lipid profile periodically starting in childhood.
Genetic counseling: WASHC5-related RSS is inherited in an autosomal recessive manner; CCDC22-related RSS is inherited in an X-linked manner.
Autosomal recessive inheritance. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier.
X-linked inheritance. If the mother of the proband has a CCDC22 pathogenic variant, the chance of transmitting it in each pregnancy is 50%. Males who inherit the pathogenic variant will be affected; females who inherit the pathogenic variant will be heterozygotes (carriers) and will usually not be affected.
Once the causative pathogenic variant(s) have been identified in an affected family member, prenatal and preimplantation genetic testing are possible.
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