Summary about Disease
X-linked intellectual disability Claes-Jensen type (XLID-CJ), also known as mental retardation, X-linked 99 (MRX99), is a rare genetic disorder primarily affecting males. It is characterized by intellectual disability, often moderate to severe, along with distinct facial features and other variable physical and neurological findings.
Symptoms
Symptoms can vary in severity but often include:
Intellectual disability (ranging from mild to severe)
Distinct facial features, which may include:
High forehead
Prominent supraorbital ridges (brow bones)
Deep-set eyes
Large ears
Thick lower lip
Behavioral problems (e.g., hyperactivity, aggression, autistic-like features)
Seizures (in some individuals)
Speech delay or absence
Motor delays
Short stature
Skeletal abnormalities (e.g., scoliosis)
Genital anomalies (e.g., cryptorchidism)
Causes
XLID-CJ is caused by mutations in the KDM5C gene, located on the X chromosome. The *KDM5C* gene provides instructions for making a protein called lysine demethylase 5C. This protein is involved in regulating gene expression and is important for brain development and function. Because males have only one X chromosome, a mutation in the *KDM5C* gene results in the full expression of the disorder. Females, who have two X chromosomes, can be carriers of the mutation. While some females carriers show no symptom, a few may present with only mild symptoms due to X-chromosome inactivation.
Medicine Used
There is no specific cure for XLID-CJ. Treatment is symptomatic and supportive, aiming to manage specific symptoms and improve the individual's quality of life. The following may be used:
Anti-seizure medications: To control seizures, if present.
Behavioral therapies: Applied behavior analysis (ABA) and other therapies to address behavioral issues and improve adaptive skills.
Speech therapy: To improve communication skills.
Physical and occupational therapy: To address motor delays and improve physical function.
Medications for ADHD: Stimulants or other medications to manage hyperactivity and attention deficits.
Is Communicable
No, X-linked intellectual disability Claes-Jensen type is not communicable. It is a genetic disorder caused by a gene mutation and cannot be spread from person to person.
Precautions
Since XLID-CJ is a genetic condition, there are no specific precautions to prevent it in individuals already affected. Genetic counseling and testing are important for families with a history of the disorder to understand the risk of recurrence and to make informed reproductive decisions.
How long does an outbreak last?
XLID-CJ is not an infectious disease and does not involve outbreaks. It is a chronic, lifelong condition resulting from a genetic mutation.
How is it diagnosed?
Diagnosis typically involves:
Clinical evaluation: Assessment of the individual's symptoms, including intellectual disability, facial features, and other physical findings.
Family history: Review of the family's medical history to identify other affected individuals.
Genetic testing: Sequencing of the KDM5C gene to identify disease-causing mutations. Chromosomal microarray analysis is sometimes used to exclude other potential causes of intellectual disability.
Neuroimaging: MRI of the brain to assess for structural abnormalities (may be normal or show non-specific findings).
Timeline of Symptoms
The timeline of symptoms can vary:
Early infancy: Motor delays, feeding difficulties may be observed.
Toddlerhood: Speech delay becomes evident. Intellectual disability is noticeable as developmental milestones are missed.
Childhood: Distinct facial features become more apparent. Behavioral problems (e.g., hyperactivity, aggression) may emerge. Seizures, if present, typically start in childhood.
Adolescence/Adulthood: The condition persists throughout life, requiring ongoing support and management.
Important Considerations
Genetic Counseling: Crucial for families to understand the inheritance pattern and recurrence risk.
Early Intervention: Early diagnosis and intervention are essential to maximize the individual's potential.
Multidisciplinary Care: Requires a team of specialists, including pediatricians, neurologists, geneticists, therapists, and educators.
Support Groups: Connecting with other families affected by XLID-CJ can provide valuable emotional support and information.
Carrier Testing: Females with a family history of XLID-CJ may choose to undergo carrier testing to determine their risk of having affected children.