Clinical and genetic heterogeneity in myotonic dystrophies.
This review of myotonic dystrophies primarily concentrates on the clinical and genetic findings that can distinguish a novel form of myotonic dystrophy, myotonic dystrophy type 2 (DM2); proximal myotonic myopathy (PROMM); and proximal myotonic dystrophy (PDM) from myotonic dystrophy type 1 (DM1). The multisystemic nature of these disorders leads to a spectrum of symptoms and signs. Careful clinical evaluation of patients with DM2/PROMM shows that the similarities among the multisystemic myotonic disorders outweigh the differences. An important point in the comparison of the phenotypes of DM1 and DM2/PROMM is that no severe congenital type of DM2/PROMM has yet been described. Genetic linkage analyses show that myotonic dystrophies can be divided into three types: the conventional Steinert type linked to chromosome 19q13.3 (DM1); DM2/PROMM and PDM linked to chromosome 3q21.3; and families not linked to either chromosomal site. Although the diagnosis may be clinically suspected, it depends on DNA analysis.
Meola
G
G
Dipartimento di Neurologia, Istituto Policlinico San Donato, Università di Milano, Via Morandi, 30, 20097 San Donato Milanese, Milano, Italy. giovanni.meola@unimi.it
D002874:Chromosome Mapping; D002888:Chromosomes, Human, Pair 19; D002893:Chromosomes, Human, Pair 3; D003937:Diagnosis, Differential; D006801:Humans; D009223:Myotonic Dystrophy / Q000145:classification / Q000235:genetics* / Q000503:physiopathology*