1 research outputs found
Muscle pathology in myotonic dystrophy: light and electron microscopic investigation in eighteen patients
Myotonic dystrophy (DM) is the most common muscular dystrophy in adults.
Two known genetic subtypes include DM1 (myotonic dystrophy type 1) and
DM2 (myotonic dystrophy type 2). Genetic testing is considered as the only
reliable diagnostic criterion in myotonic dystrophies. Relatively little is known
about DM1 and DM2 myopathology. Thus, the aim of our study was to characterise
light and electron microscopic features of DM1 and DM2 in patients with
genetically proven types of the disease. We studied 3 DM1 cases and 15 DM2
cases from which muscle biopsies were taken for diagnostic purposes during
the period from 1973 to 2006, before genetic testing became available at our
hospital. The DM1 group included 3 males (age at biopsy 15–19). The DM2
group included 15 patients (5 men and 10 women, age at biopsy 26–60). The
preferential type 1 fibre atrophy was seen in all three DM1 cases in light microscopy,
and substantial central nucleation was present in two biopsies.
Electron microscopy revealed central nuclei in all three examined muscle biopsies.
No other structural or degenerative changes were detected, probably due to the
young age of our patients. Central nucleation, prevalence of type 2 muscle fibres,
and the presence of pyknotic nuclear clumps were observed in DM2 patients in
light microscopy. Among the ultrastructural abnormalities observed in our DM2
group, the presence of internal nuclei, severely atrophied muscle fibres, and lipofuscin
accumulation were consistent findings. In addition, a variety of ultrastructural
abnormalities were identified by us in DM2. It appears that no single ultrastructural
abnormality is characteristic for the DM2 muscle pathology. It seems, however,
that certain constellations of morphological changes might be indicative of
certain types of myotonic dystrophy. (Folia Morphol 2011; 70, 2: 121–129