How Common is Angelman Syndrome?

The prevalence of Angelman syndrome (AS) can be estimated by using multiple sources of information such as medical practitioner records, hospital registries, laboratory test records and information from schools, public health facilities and developmental institutions.  One of the earliest studies came from Denmark where children with the diagnosis of AS, determined from medical clinic records, were compared to an 8-year period having 45,000 births and showed a minimum AS prevalence of about 1/10,000 (Petersen et al., 1995). Another study of school age children, ages 6-13 years, living in Sweden showed an AS prevalence of about 1/12,000  (Steffenburg et al., 1996).


Several reports address the prevalence of AS among groups of individuals with established developmental delay and found varying rates of 0%  (Vercesi et al., 1999), 1.3% (Aquino et al., 2002), 1.4% (Jacobsen et al., 1998), and 4.8% (Buckley et al., 1998).

The  Buckley paper extrapolated their data in order to compare it to the population of the state of Washington (using 1997 U.S. Census data) and obtained an estimate of 1/20,000, a number similar to that often quoted (Clayton-Smith and Pembrey, 1992).

A more recent Danish study used a relatively complete multiple ascertainment method to identify 51 individuals with genetically verified AS who were born between 1991 and 2009 (Mertz et al., 2013).  During this time there were approximately 1,254,000 births in Denmark.  The birth incidence was estimated to be about 1/24,500.  The authors felt the rate might be as low as approximately 1/23,000, as there are some individuals with apparent AS who have negative genetic testing.

Thus, it appears that about 1/12,000 to 1/24,000 children will have AS.  We are learning more about the natural history of AS and much remains to be determined.  In the future, it may be possible, through the newborn blood screening for example, to identify most babies born with AS.  Also, the Angelman community would benefit from an analysis of all known AS deaths  (accidental and non-accidental).   It would also be helpful to track individuals with AS in the geriatric years.  Results of these analyses will better inform us about the natural history of AS.

Charles Williams, M.D. is a Professor of Pediatrics and Genetics, Division of Genetics and Metabolism, Department of Pediatrics, University of Florida.


Aquino NH, Bastos E, Fonseca LC and others. 2002.  Genet Test 6(2):129-31.

Buckley RH, Dinno N, Weber P. 1998.  Am J Med Genet 80(4):385-90.

Clayton-Smith J, Pembrey ME. 1992.  J Med Genet 29(6):412-5.

Jacobsen J, King BH, Leventhal BL and others. 1998.  J Med Genet 35(7):534-8.

Mertz LG, Christensen R, Vogel I and others. 2013.  Am J Med Genet A 161(9):2197-203.

Petersen MB, Brondum-Nielsen K, Hansen LK and others. 1995.  Am J Med Genet 60(3):261-2.

Steffenburg S, Gillberg CL, Steffenburg U and others. 1996.  Pediatr Neurol 14(2):131-6.

Vercesi AM, Carvalho MR, Aguiar MJ and others. 1999.  J Med Genet 36(6):498.