(mentions CMT/HMSN) Prevalence of genetic muscle disease in Northern England: i

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Brain. 2009 Sep 18.

Prevalence of genetic muscle disease in Northern England: in-depth analysis of a

muscle clinic population.

Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V.

1 Institute of Human Genetics, Newcastle University, Newcastle upon Tyne NE1

3BZ, UK.

We have performed a detailed population study of patients with genetic muscle

disease in the northern region of England. Our current clinic population

comprises over 1100 patients in whom we have molecularly characterized 31

separate muscle disease entities.

Diagnostic clarity achieved through careful delineation of clinical features

supported by histological, immunological and genetic analysis has allowed us to

reach a definitive diagnosis in 75.7% of our patients. We have compared our case

profile with that from Walton and Nattrass' seminal study from 1954, also of the

northern region, together with data from other more recent studies from around

the world.

Point prevalence figures for each of the five major disease categories are

comparable with those from other recent studies.

Myotonic dystrophies are the most common, comprising 28.6% of our clinic

population with a point prevalence of 10.6/100 000. Next most frequent are the

dystrophinopathies and facioscapulohumeral muscular dystrophy making up 22.9%

(8.46/100 000) and 10.7% (3.95/100 000) of the clinic population, respectively.

Spinal muscular atrophy patients account for 5.1% or 1.87/100 000 patients. Limb

girdle muscular dystrophy, which was described for the first time in the paper

by Walton and Nattrass (1954) and comprised 17% of their clinic population,

comprises 6.2% of our clinic population at a combined prevalence of 2.27/100

000.

The clinic population included patients with 12 other muscle disorders. These

disorders ranged from a point prevalence of 0.89/100 000 for the group of

congenital muscular dystrophies to conditions with only two affected individuals

in a population of three million.

For the first time our study provides epidemiological information for X-linked

Emery-Dreifuss muscular dystrophy and the collagen VI disorders. Each of the

X-linked form of Emery-Dreifuss muscular dystrophy and Ullrich muscular

dystrophy has a prevalence of 0.13/100 000, making both very rare. Bethlem

myopathy was relatively more common with a prevalence of 0.77/100 000. Overall

our study provides comprehensive epidemiological information on individually

rare inherited neuromuscular conditions in Northern England.

Despite the deliberate exclusion of relatively common groups such as hereditary

motor and sensory neuropathy (40/100 000) and mitochondrial disorders (9.2/100

000), the combined prevalence is 37.0/100 000, demonstrating that these

disorders, taken as a group, encompass a significant proportion of patients with

chronic disease.

The study also illustrates the immense diagnostic progress since the first

regional survey over 50 years ago by Walton and Nattrass.