Clinical pathological and genetic analysis of 2 cases of mitochondrial myopathy presented as acute motor axonal neuropathy

Abstract

Background The main clinical manifestations of mitochondrial myopathy are chronic limb weakness and muscular soreness. Subclinical peripheral nerve injury is also reported, but acute axonal neuropathy.like syndrome concurrent with lactic acidosis is rare. In this paper the clinical features of 2 patients presenting as acute lactic acidosis and sudden muscle weakness were analyzed. Pathological changes and genetic mutations were detected.  Methods Electromyography (EMG) and muscle biopsy were performed. Modified Gomori trichrome (MGT) and succinodehydrogenase (SDH) staining were used to identify pathological changes. Changes of ultra microstructure of muscular tissue were observed under electron microscope. Mitochondrial DNA (mtDNA) full length sequencing was performed using 24 pairs of partially overlapping primers.  Results EMG showed a coexistence of neurogenic and myogenic changes. Dramatic decrease of motor nerve amplitude and moderately reduced sensory nerve amplitude were observed but nerve conduction velocity was normal in both patients. Impressive ragged red fibers were seen on MGT staining. Electron microscope showed dramatic mitochondrial abnormalities in Case 1 and paracrystaline inclusions in Case 2. mtDNA sequencing showed 3243A > G mutation in Case 1 and 8344A > G mutation in Case 2. Conclusions Mitochondrial myopathy can present as metabolic crisis like acute lactic acidosis, dyspnea and acute motor axonal neuropathy.like syndrome. It is a life.threatening phenotype that needs more attention.

doi: 10.3969/j.issn.1672-6731.2014.06.007