International CDKL5 Day Date in the current year: June 17, 2025

The CDKL5 gene, originally named STK9, encodes the protein cyclin-dependent kinase-like 5 (CDKL5), which plays a critical role in early brain development. Mutations in this gene cause CDKL5 deficiency disorder (CDD), which is characterized by developmental delay, intellectual disability, motor impairment, and seizures.

Since the CDKL5 gene is located on the X chromosome, females are more frequently diagnosed than males. Since females have two X chromosomes, a mutation in one copy of the CDKL5 gene is enough to cause CDD. However, the unaffected copy of the gene can offer some compensation, ensuring that girls with CDD live long enough to be diagnosed. Males have only one X chromosome, so there is no chance of compensation; many boys with CDD die before receiving a formal diagnosis.

In short, females are more frequently diagnosed with CDD because they are more likely to survive with the condition. In contrast, the mutation’s effects are often too severe for survival in males, which skews the apparent prevalence toward females. Nearly all mutations are de novo (spontaneous) rather than inherited, as CDD patients are unlikely to have children due to their profound neurodevelopmental disabilities. CDD is an extremely rare disorder, with fewer than 1,000 diagnosed cases worldwide.

Seizures are the earliest symptom of CDD. They typically begin within a few months after birth and do not respond well to medication. Other early symptoms include feeding and sleeping problems, teeth grinding, and gastrointestinal issues such as air swallowing, constipation, and reflux. Additional symptoms include delayed development of gross motor skills (such as sitting, standing, and walking), restricted fine motor skills, repetitive hand movements, low muscle tone (hypotonia), intellectual disability (often accompanied by little or no speech), and visual impairment.

There is no cure for CDD. Anticonvulsants are used to control seizures, though those associated with the disorder are usually resistant to medication. Medications may also be prescribed to address sleep and gastrointestinal issues. Patients also benefit from physical, occupational, and vision therapy. The long-term prognosis and average life expectancy for patients with CDD are unclear because the disorder is rare and was discovered just over two decades ago.

International CDKL5 Day is observed on June 17 in honor of Glyn Boltwood, who passed away on this day in 1997. His DNA was key to discovering CDD. The gene responsible for Glyn’s seizures and developmental delay was discovered in 2004 by an Australian research team led by John Christopodoulou, who originally thought the disorder to be a variant of Rett syndrome.

The main goals of International CDKL5 Day are to raise awareness of this rare disorder, support patients with CDD and their families, provide them with necessary resources, and promote research into CDD.