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. Author manuscript; available in PMC: 2015 Jul 7.
Published in final edited form as: Genet Med. 2001 Sep-Oct;3(5):359–371. doi: 10.1097/00125817-200109000-00006

Table 1.

Prevalence of the fragile X syndrome among males determined by DNA-based techniques adapted from 8

Country Target population No. positive/ No.
tested		 Estimated prevalence
Target Population
%		 General Population
(95% CI)
U.K.
(Wessex)41;121 		SpEd population
(ages 5–18 years),
unknown etiology		 20/3,738 SpEd: 0.5 1/5,530
(1/8,992–1/4,007)
U.S.A.
(Atlanta, Georgia)38;122 		SpEd population
(ages 7–10 years),
regardless of
etiology		 Caucasian: 4/1,572

African-American: 3/752		 Caucasian SpEd: 0.3

African-American SpEd: 0.4		 Caucasian: 1/3,717
(1/7,692–1/1,869)

African-American: 1/2,545
(1/5,208–1/1,289)
Southwest Netherlands 47 Schools and
institutes for MR,
unknown etiology		 9/866 Mild MR: 2.0
Moderate/ severe MR: 2.4		 1/6,045
(1/9,981–1/3,851)
Hellenic population of
Greece and Cyprus 40 		Referred clinical
population of
idiopathic MR		 8/611 MR: 1.3 1/4,246
(1/16,440–1/1,333)
Australia
(Sydney) 36;37 		Children with MR in
SpEd		 10/472 MR: 2.1
Mild MR: 0.6
Moderate/ severe MR: 5.4		 1/4,350b
France123 Children with
DSM-IIIR
classification of MR		 10/403 MR: 2.5
Mild MR: 1.4
Moderate/ severe MR: 3.6		 -
U.S.A.
(Baltimore, Maryland) 46 		Preschool children
referred for language
delay		 1/379 Language delay: 0.3 -
China
(mainland and Hong
Kong)124 		Persons with MR
clinically referred or
in SpEd		 31/902a MR: 3.4 -
India (Delhi) 125 Clinically referred
children with MR,
unknown etiology		 19/360 MR: 5.3 -
Southern Häme, Finland
126 		Adult males (>16
years) registered in
the Southern Häme
Care Organization
with MR, unknown
etiology		 6/344 MR: 1.7 1/4,400c
Finland 45 Clinically referred
persons with MR		 15/305 MR: 4.9 -
U.S.A.
(Colorado)127 		Targeted “high risk”
children (ages 2–18
years with MR,
autism, LD, ADHD,
family history) in
SpEd population		 1/299 SpEd: 0.3 -
Japan 128 Institutionalized
persons with MR		 8/298 MR: 2.7 -
Indonesia
(primarily Javanese)129 		Schools for mild
developmental
delay, no cytogenetic
abnormality		 5/262 Mild MR: 1.9 -
Hellenic population of
Greece and Cyprus 130 		Referred clinical
population of
idiopathic MR		 4/257 MR: 1.6
Moderate/ severe MR: 2.9
Profound MR: 3.6		 -
Brazil
131 		Schools for the
mentally disabled		 5/256 MR: 2.0
Mild MR: 2.3
Severe MR: 1.6		 -
Japan 132 Males with MR or
psychomotor
developmental
delay, clinically
referred		 2/256 MR: 0.8 -
Singapore 133 Children in schools
for mild to severe
MR, unknown
etiology		 5/254 MR: 2.0 -
Hong Kong 134 Persons with mild
MR, unknown
etiology		 1/243 Mild MR: 0.4 -
U.K.
(Coventry)35;37;135 		Children with MR in
institutions or SpEd		 6/219 MR: 2.7
Mild MR: 1.3
Moderate/ severe MR: 6.7		 1/4,090d
Chile 136 Children in SpEd
with MR of
unknown etiology;
excluded profound
MR		 4/214 MR: 1.9 -
Taiwan 137 Persons with MR of
unknown etiology
enrolled in SpEd or
private day-care
centers		 4/206 MR: 1.9
Mild MR: 3.8
Moderate/ severe MR: 0.8		 -
Poland
(Warsaw)42 		Males in institutions
or SpEd with MR		 6/201 MR: 3.0 1/2,857–1/5,882e
Southwest Netherlands 138 Clinically referred
persons with MR and
no known family
history of fragile X		 10/197 MR: 5.1 -
U.S.A.
(New Mexico)139 		Clinically referred
persons with MR or
behavior disorders,
unknown etiology		 10/188 MR: 3.7
LD: 1.1
Hyperactivity/AD: 0.5		 -
Spain 140 Persons with MR in
SpEd		 11/182 MR: 6.0 -
U.K.
(Wessex)39 		SpEd population
(ages 5–18 years),
unknown etiology		 4/180 SpEd: 2.2 1/8,918f
Spain 43 Children in SpEd or
clinically referred
with MR of
unknown etiology;
no known family
history of MR		 5/180 MR: 2.7 1/6,200–1/8,200g
Turkey 141 Clinically referred
children with
developmental
disability		 5/166 MR: 3.0 -
Guadeloupe, French West
Indies 56 		SpEd population,
unknown etiology		 11/163 SpEd: 6.7 1/2,359 (1/4,484–1/276)
South Africa 142;143 Institutionalized
males (blacks) with
idiopathic MR		 9/148 MR: 6.1
Mild MR: 4.2
Severe MR: 7.8		 -
U.K.144 Institutionalized
males with learning
disabilities,
unknown etiology		 1/138 LD: 0.7 -
U.K.
(Oxfordshire)44 		Children in schools
for moderate to
severe learning
difficulties,
unknown etiology		 4/103 MR: 3.9 1/4,130h
Thailand 145 Children with
developmental delay
or MR, unknown
etiology		 5/94 MR: 5.3 -
India
(New Delhi)146 		Institutionalized
persons with MR
with unknown
etiology that scored
above 40% on a
fragile X checklist
147 		9/93 MR: 9.7 -
Spain 53 Persons in
institutions or SpEd
with idiopathic MR		 8/92 MR: 8.7 -
Brazil 148 Institutionalized
persons with severe
MR, unknown
etiology		 0/83 - -
Croatia 149 Children clinically
preselected for
fragile X DNA
analysis on the basis
of MR of unknown
etiology, a positive
family history, and at
least on physical
and/or behavioral
characteristic of the
fragile X syndrome		 14/81 17.3 -
Mexico 150 Children clinically
referred with MR,
unknown etiology		 2/53 MR: 3.8 -

Abbreviations: Special education or special schools (SpEd), mental retardation (MR), learning disability (LD), attention deficit/hyperactivity disorder (ADHD), attention deficit (AD).

a

Zhong et al.124 did not distinguish between males and females in the published manuscript. The numbers presented in table 1 are derived from personal communication with Dr. Zhong.

b

Turner et al.37 provided on a point estimate.

c

Arvio et al.126 provided only a range on the basis of past cytogenetic and DNA-based diagnoses.

d

Morton et al.135 provided only a point estimate.

e

Mazurczak et al 42 provided only a range, not a point estimate.

f

Jacobs et al 39 provided only a point estimate.

g

Millan et al 43 provided a range, not a point estimate. Millan et al 43 also acknowledged that persons with mild MR might have been missed, so the range could be as high as 1/5,000–1/6,800.

h

Slaney et al 44 only provided a lower boundary, not a point estimate.