Jacobsen syndrome


A very rare chromosomal disorder involving the absence of a portion of chromosome 11q. The range and severity of symptoms is determined by the size of the portion that is deleted.


  • Congenital heart defects 
  • Thrombocytopenia 
  • Mental retardation 
  • Cognitive dysfunction 
  • Impaired expressive language use 
  • Eye symptoms 
  • Gastrointestinal symptoms 
  • Short stature 
  • Genitourinary problems 
  • Delayed motor skills 
  • Severe platelet dysfunction 
  • Increased risk of bleeding 
  • Retarded growth 
  • Psychomotor retardation 
  • Trigonocephaly 
  • Strabismus 
  • Epicanthus 
  • Telecanthus 
  • Broad nose bridge 
  • Short nose 
  • Anteverted nostrils 
  • Carp-shaped upper lip 
  • Small jaw 
  • Low set ears 
  • Abnormal ear shape 
  • Camptodactyly 
  • Hammertoes 
  • Short thumb 
  • Abnormal thumb position 
  • Narrow chest 
  • Diastasis recti 
  • Abnormal anal position 
  • Low blood sugar 
  • Pancytopenia 
  • Osteopenia
  • Hearing loss 
  • Osteoporosis 
  • Narrowed urethra 
  • Partial corpus callosum agenesis


Most individuals with Jacobsen syndrome are diagnosed after birth. The diagnosis is usually made through a blood test called chromosome analysis in an infant or child who has mental retardation and a typical facial appearance. The karyotype will show a deletion or rearrangement of the longer segment, known as the q arm, of one copy of chromosome 11. Jacobsen syndrome can be diagnosed before birth. There have been reports of prenatal diagnosis through amniocentesis after an ultrasound demonstrated one or more fetal abnormalities. Another technique, known as FISH (fluorescent in-situ hybridization), may be used to further define the chromosome 11q deletion breakpoints; this laboratory test is being done on a research basis to identify the disease-causing genes in the Jacobsen syndrome critical region.


Approximately 25% of affected children die before two years of age mainly from cardiac defects, a tendency to bleed, or infection. Except for respiratory infections, the remainder of children are generally healthy. Most individuals described here are children or adolescents. Little is known about the course of this syndrome in adulthood, and the life expectancy for those who live beyond age two is unknown.