Jacobsen Syndrome
Introduction
Jacobsen syndrome (11q deletion syndrome) is a rare chromosomal disorder caused by terminal deletion of chromosome 11q. It is characterized by intellectual disability, physical growth delay, distinctive facial features, and various medical complications.
Key Points
- Prevalence: 1/100,000 births
- Female to male ratio: 2:1
- Most cases are de novo deletions
- Variable deletion sizes (7-20Mb)
- Characteristic thrombocytopenia (Paris-Trousseau syndrome)
Clinical Features
Craniofacial Features
- Skull Abnormalities:
- Trigonocephaly
- Prominent forehead
- Craniosynostosis
- Facial Features:
- Hypertelorism
- Downslanting palpebral fissures
- Short nose with flat bridge
- Small mandible
- Low-set, malformed ears
- Thin upper lip
- High-arched palate
Developmental Features
- Growth:
- Pre- and postnatal growth retardation
- Short stature
- Feeding difficulties
- Development:
- Global developmental delay
- Mild to moderate intellectual disability
- Speech delay
- Motor delays
- Behavioral issues
Diagnosis
Genetic Testing
- Primary Testing Methods:
- Chromosome microarray analysis
- FISH analysis
- Karyotype
- Next-generation sequencing
- Additional Assessments:
- Complete blood count
- Platelet function studies
- Cardiac evaluation
- Brain imaging
Differential Diagnosis
- Other chromosomal deletion syndromes
- Isolated trigonocephaly
- Other causes of thrombocytopenia
- Noonan syndrome
- Turner syndrome
Management
Medical Management
- Hematological Care:
- Regular platelet monitoring
- Transfusion protocols
- Bleeding precautions
- Cardiac Care:
- Regular cardiac evaluations
- Management of congenital heart defects
- Endocarditis prophylaxis if indicated
- Growth and Development:
- Growth hormone therapy if indicated
- Feeding support
- Nutritional management
Therapeutic Interventions
- Early Intervention:
- Physical therapy
- Occupational therapy
- Speech therapy
- Special education services
- Behavioral Support:
- Behavioral therapy
- Social skills training
- Educational support
Genetics & Cytogenetics
Genetic Basis
- Chromosome Region: 11q23.3-11qter
- Deletion Characteristics:
- Terminal deletions
- Variable size (7-20Mb)
- Critical region: 11q24.1
- Important Genes:
- FLI1 (thrombocytopenia)
- KCNJ1 (cardiac defects)
- NFRKB (neurological features)
- JAM3 (developmental aspects)
Inheritance Pattern
- Most cases are de novo
- Rare inherited cases from balanced translocation carriers
- Recurrence risk assessment needed
Complications & Monitoring
Major Medical Complications
- Hematological:
- Paris-Trousseau syndrome
- Thrombocytopenia
- Platelet dysfunction
- Cardiac:
- Ventricular septal defects
- Left heart obstruction
- Other structural defects
- Neurological:
- Seizures
- Behavioral problems
- Sleep disturbances
Monitoring Protocol
- Regular Health Surveillance:
- Annual physical examination
- Growth monitoring
- Development assessment
- CBC with platelet count
- Cardiac evaluations
Prognosis & Support
Long-term Outlook
- Variable prognosis based on:
- Deletion size
- Severity of complications
- Early intervention success
- Life Expectancy:
- Reduced in severe cases
- Better with modern medical care
- Dependent on cardiac/bleeding complications
Support Resources
- Family Support:
- Genetic counseling
- Support groups
- Educational advocacy
- Social services
- Transition Planning:
- Educational planning
- Vocational training
- Adult healthcare transition
