Clin Genet 2001: 59: 344–349
Printed in Ireland. All rights resered
Short Report
Epidemiology of myotonic dystrophy in
Italy: re-apprisal after genetic diagnosis
Siciliano G, Manca ML, Gennarelli M, Angelini C, Rocchi A, Iudice
A, Miorin M, Mostacciuolo ML. Epidemiology of myotonic dystrophy
in Italy: re-apprisal after genetic diagnosis.
Clin Genet 2001: 59: 344–349. © Munksgaard, 2001
Before the discovery of the myotonic dystrophy (DM) gene, the DM
epidemiological rates could not be accurately estimated. The aim of
this study was to calculate the DM prevalence rates in Padova (North-
East Italy) and in four provinces of North-West Tuscany (Central
Italy) and, as of 30 June 1999, to do so using molecular genetic testing.
A minimum prevalence rate of 9.31 ×10
-5
inhabitants was found, con-
sistent with epidemiological rates worldwide, and more than two times
as high as those of two previous studies conducted in the same areas
during the era prior to molecular genetic testing.
This study, the first in Italy since the discovery of the DM gene, under-
lines the importance of direct genetic diagnosis of DM, especially in
detecting mildly affected patients, a fundamental step in correctly esti-
mating the risk of disease transmission in affected families.
G Siciliano
a
, ML Manca
a
,
M Gennarelli
b
, C Angelini
c
,
A Rocchi
a
, A Iudice
a
, M Miorin
d
and ML Mostacciuolo
d
a
Department of Neuroscience, University of
Pisa, Pisa,
b
Human Genetics Laboratory,
IRCCS-Fatebenefratelli, Brescia,
c
Department of Neurological and
Psychiatric Sciences and
d
Department of
Biology, University of Padova, Padova, Italy
Key words: epidemiology – genetic
diagnosis – myotonic dystrophy
Corresponding author: Dr Gabriele Siciliano,
M.D., Ph.D., Department of Neuroscience,
Neurological Clinics, Via Roma 67, 56126
Pisa (I), Italy. Tel: +39-050-993046/
993334; fax: +39-050-554808/550563;
e-mail: gsicilia@med.unipi.it
Received 1 November 2001, revised and
accepted for publication 16 January 2001
Myotonic dystrophy (DM) is an autosomal domi-
nant multisystem disorder characterized by myoto-
nia, muscle atrophy, blepharoptosis, frontal
balding, cataracts, gonadal atrophy, cardiomyopa-
thy and mental impairment (1). The onset age and
disease severity show marked variability both be-
tween and within families. The cloning of the DM
gene and identification of the mutation offer the
possibility of direct gene testing, which improves
clinical diagnostic accuracy. The genetic defect
results from an unstable CTG trinucleotide repeat
in the 3 non-coding region of the DM protein
kinase gene (DMPK) mapped on chromosome
19q13.3. In the normal population, the number of
CTG repeats varies between 5 and 36 triplets,
while from 50 to several thousand copies have been
observed in DM patients (2). The (CTG) expan-
sion is unstable at mitotic and meiotic levels, with
a bias towards length increase in the successive
generations, which accounts for the clinical antici-
pation. In fact, the size of the trinucleotide repeat
is related to onset age and clinical severity of
disease (3).
DM is the most frequent muscular dystrophy in
adulthood with a prevalence rate of 2.2–5.5 per
100000 inhabitants in Western Europeans (1) and
5.5 per 100000 inhabitants in the Japanese popula-
tion (4). DM is less prevalent in South-East Asian
populations and is rare or absent in Africans (5).
For the Italian population, only few reports are
available on the epidemiology of DM, two of them
performed in the same areas as in this study, and
finding prevalence rates of 3.6 in the Veneto region
(North-East Italy) (6) and 3.4 in North-West Tus-
cany (Central Italy) (7), respectively. All these re-
ports are antecedent to DM gene discovery.
Therefore, we describe here a re-evaluation of DM
prevalence rates in those two population samples
of the Veneto and Tuscany regions using DNA
analysis for DM mutation.
Materials and methods
Methods of ascertainment
The ascertainment of all cases of MD in the two
areas under consideration was carried out as
follows:
344