Wiedemann-Steiner syndrome. WSS. Growth deficiency and mental retardation with facial dysmorphism
Incidence
Wiedemann–Steiner syndrome results from mutations in the MLL (also known as KMT2A) gene on the long arm of chromosome 11. A few hundred people have been documented with the condition worldwide. Once thought to have an incidence of 1 in 1,000,000, some research has suggested the incidence may be as high as 1 in 40,000. The condition is autosomal dominant, meaning that only one abnormal copy of the gene is needed for a person to have the syndrome. In a majority of cases to date, the mutation occurred de novo.
Clinical Characteristics
Wiedemann-Steiner syndrome is a congenital malformation syndrome characterized by hypertrichosis cubiti associated with short stature; consistent facial features, including long eyelashes, thick or arched eyebrows with a lateral flare, wide nasal bridge, and downslanting and vertically narrow palpebral fissures; mild to moderate intellectual disability; behavioral difficulties; and hypertrichosis on the back. Features described in Wiedemann–Steiner syndrome include: short stature, developmental delay, low muscle tone (hypotonia) especially in infancy, characteristic facial features and hairy elbows (hypertrichosis cubiti). It has a variable clinical phenotype with additional manifestations reported including muscular hypotonia, patent ductus arteriosus, small hands and feet, hypertrichosis on the back, behavioral difficulties, and seizures. Constipation is very common.
Precipitants
None. Patients have no crisis reported.
Provocation Tests
None.
Diagnostic Procedures
If Wiedemann–Steiner syndrome is suspected, analysis of the MLL gene can be carried out. Otherwise, it may be diagnosed by whole-exome sequencing or whole genome sequencing. Whole exome sequencing has been used to identify most people with WSS. Most patients have been labeled with different clinical diagnosis until the mutation is discovered.