Summary
Jacobsen syndrome is a multiple congenital anomaly/mental retardation (MCA/MR) contiguous gene syndrome caused by partial deletion of the long arm of chromosome 11. To date, over 200 cases have been reported in the literature. The prevalence is estimated at 1/100,000 births, with a female/male ratio of 2:1. The most common clinical features include pre- and postnatal growth retardation, psychomotor retardation, and a characteristic facial dysmorphism (skull deformities, hypertelorism, ptosis, coloboma, downslanting palpebral fissures, epicanthal folds, a broad nasal bridge, short nose, V-shaped mouth, and small, low-set and posteriorly rotated ears). Abnormal platelet function, thrombocytopenia or pancytopenia are usually present at birth. Patients commonly have malformations of the heart, kidney, gastrointestinal tract, genitalia, central nervous system and skeleton. Ocular, auditory, immunological and hormonal anomalies may be also present. The deletion size ranges from ~7 to 20Mb, with the proximal breakpoint within or telomeric to subband 11q23.3 and the deletion usually extending to the telomere. The deletion occurs de novo in 85% of reported cases, and in 15% of cases it results from an unbalanced segregation of a familial balanced translocation or from other chromosome rearrangements. In a minority of cases the breakpoint is at the FRA11B fragile site. Diagnosis is based on clinical findings (intellectual deficit, facial dysmorphism and thrombocytopenia) and confirmed by cytogenetic analysis. Differential diagnoses include the Turner and Noonan syndromes (see these terms), and acquired thrombocytopenia due to sepsis. Prenatal diagnosis of 11q deletion is possible through cytogenetic analysis of amniocytes or chorionic villus samples. Management is multi-disciplinary and requires evaluation by a pediatrician, pediatric cardiologist, neurologist and ophthalmologist. Auditory tests, blood tests, endocrine and immunological assessment and follow-up should be offered to all patients. Cardiac malformations can be very severe and require heart surgery in the neonatal period. Newborns with Jacobsen syndrome may have feeding difficulties and tube feeding may be necessary. Special attention should be devoted to hematological problems. About 20% of children die during the first two years of life, most commonly due to complications from congenital heart disease, and less commonly from bleeding. For patients who survive the neonatal period and infancy, the life expectancy remains unknown. *Authors: Drs T. Mattina, C.S. Perrotta, P. Grossfeld (March 2009)*. Reproduced from Jacobsen syndrome. Orphanet J Rare Dis. 2009; 4:9.
