Objective: To investigate the clinical, pathological and ultrastructural features of nemaline myopathy (NM).
Methods: The clinical manifestations of four patients in a rare autosomal recessive kindred with nemaline myopathy were analyzed retrospectively. Biopsied specimens of left gastrocnemius from the proband were detected and observed through light microscope using enzymatic histochemical methods for histopathological changes and through electron microscope for ultrastructural features.
Results: Four affected siblings in this kindred had an onset at birth or fetal stage, among whom two case were respiratory independent with delayed attainment of motor milestones and general muscle atrophy complying with typical form of NM, whereas the other two did not achieve adequate spontaneous movement or breathing, and died at neonatal period according with severe form of NM. Other clinical characteristics of elongated face, tent-shaped mouth and high-arched palate were also found. The proband had normal serum muscle enzymes and the karyotypic analysis showed a normal G band. Brain magnetic resonance image (MRI) indicated no abnormality. Electromyogram (EMG) showed typical muscle-derived damages of biceps, triceps, brachioradial muscle, vastus medialis muscle, anterior tibial muscle and gastrocnemius with normal motor conduction velocity of bilateral tibial nerves and common peroneal nerves. Myofibrillar atrophy was found through light microscopy with fiber type 1 predominance shown by ATP enzyme staining, yet without indication of lipid or glycogen deposition by ORO or PAS staining. Modified gomori trichrome (MGT) treatment resulted in dark-red staining of nemaline bodies in myofibril cytoplasm. And it was also observed as purple-red staining followed by hematoxylin-eosin (HE) treatment. Electron microscopic observation by lead-uranium double staining showed widened interstitial myofibrils, focal myofilament disorganization, partial myofilament atrophy, focal dissolution or necrosis, partial myofibrils nucleus pyknosis, numerous subsarcolemmal and perinuclear rod-like structures, partial nemaline bodies connected with Z discs, and mitochondria vacuolation or disappearance.
Conclusion: NM is among congenital myopathies characterized by marked clinical and pathological heterogeneity. The diagnosis of NM should be based upon typical clinical and histopathological features.