International WSS Awareness Day Date in the current year: September 15, 2026

The KMT2A gene encodes an enzyme of the same name that regulates cell reproduction and is active during early development and hematopoiesis, or the formation of blood cells. Mutations in this gene can result in blood cancers, neurological disorders, and a developmental disorder known as Wiedemann-Steiner syndrome (WSS).

Wiedemann-Steiner syndrome is caused by germline loss-of-function mutations in the KMT2A gene. “Germline” means the mutation was present in the DNA of a parent’s egg or sperm, rather than occurring during fetal development. “Loss-of-function” means the mutation prevents the gene from producing a functional enzyme. The condition is autosomal dominant, meaning inheriting one abnormal copy of the gene from either parent is enough for a person to develop WSS. Hans-Rudolf Wiedemann first described the syndrome in 1989, and Wendy D. Jones identified its genetic cause in 2012.

WSS symptoms are similar to those of many other neurodevelopmental disorders and include characteristic facial features, developmental delay, intellectual disability, hypotonia (low muscle tone), and short stature. Patients with WSS have distinctive facial features, including a round, flat face, a long medial cleft, a short nose with a broad bridge and bulbous tip, widely spaced eyes, thick eyebrows, long eyelashes, low-set ears, and a high-arched palate.

Excessive hair growth, particularly hypertrichosis cubiti (known as “hairy elbow syndrome”), is a characteristic feature of WSS present in more than half of patients. Other possible symptoms include congenital heart defects, renal abnormalities, skeletal abnormalities, brain abnormalities, seizures, immune dysfunction, and others.

Since WSS shares many symptoms with other genetic disorders and the clinical presentation can vary greatly between patients, the syndrome is difficult to diagnose. The exact prevalence of WSS is thus unknown, but it may be higher than suspected because the syndrome is likely underdiagnosed.

There is currently no cure for the underlying genetic cause of WSS. Management focuses on addressing specific symptoms and improving quality of life. This may include physiotherapy, speech therapy, occupational therapy, educational support, developmental and behavioral interventions, and surveillance or treatment of health problems associated with the syndrome. Therefore, management usually requires a multidisciplinary team of specialists.

International WSS Awareness Day is an initiative of the WSS community spearheaded by the Wiedemann-Steiner Syndrome Foundation, a nonprofit organization established in 2016 to support individuals and families affected by WSS. The main goals of the day are to raise awareness of the syndrome beyond the small patient and medical communities, advocate for more WSS research, and raise funds to support affected families.