Wiedemann-Steiner syndrome (WSS) includes distinctive facial features, growth delay, and intellectual disability. Signs and symptoms vary, but facial features may include thick eyebrows, wide-spaced eyes, and narrow eye openings. People with WSS may also have excessive hair on the elbows, arms, and back; difficulty feeding; behavior problems; and seizures. Because WSS has been reported in a small number of individuals, there is not much information on how the symptoms and features change over time. WSS is caused by genetic changes in the KMT2A gene. Most individuals with WSS are the only ones in their family with this condition. In a few cases, WSS has been inherited in an autosomal dominant pattern. Diagnosis is based on the symptoms and clinical exam, and it is confirmed by the results of genetic testing. Treatment is focused on managing the symptoms.

Wiedemann-Steiner syndrome occurs when the KMT2A gene is not working correctly. DNA changes known as pathogenic variants are responsible for making genes work incorrectly or sometimes, not at all.

The following list includes the most common signs and symptoms in people with Wiedemann-Steiner syndrome (WSS). These features may be different from person to person. Some people may have more symptoms than others, and they can range from mild to severe. This list does not include every symptom that has been described in the condition. Signs and symptoms may include:

• Growth delay before and after birth
• Excessive hair on the elbows, arms and/or back (hypertrichosis)
• Wide spaced eyes
• Narrow palpebral fissures
• Thick eyebrows
• Intellectual disability
• Developmental delay
• Low muscle tone (hypotonia)

Other signs and symptoms may include skeletal and eye abnormalities, feeding problems in early childhood, and seizures. Adults with WSS have been reported to have behavior issues. About 60 cases of WSS have been described in the medical literature, and little is known about how this condition changes over time.

Treatment of Wiedemann-Steiner syndrome is focused on managing the symptoms.  Specialists involved in the care of someone with Wiedemann-Steiner syndrome may include:

• Neurologist
• Gastroenterologist
• Developmental and behavioral specialists
• Medical geneticist

Wiedemann-Steiner syndrome (WSS) usually occurs due to a new genetic variant (de novo), and there is no family history of WSS. In some families, WSS has been inherited in an autosomal dominant pattern. All individuals inherit two copies of each gene. Autosomal means the gene is found on one of the numbered chromosomes found in both sexes. Dominant means that only one pathogenic variant on one copy of a gene is necessary to have the condition. The variant can be inherited from either parent. Each child of an individual with an autosomal dominant condition has a 50% or 1 in 2 chance of inheriting the variant and the condition. Typically, children who inherit a dominant variant will have the condition, but they may be more or less severely affected than their parent.  Sometimes a person may have a gene variant for an autosomal dominant condition and show no signs or symptoms of the condition.