Abstract
Axial myopathy can be the underlying cause of rapidly progressive adult-onset scoliosis; however, the pathogenesis of this disorder remains poorly understood. Here we present a case of a 69-year old woman with a family history of scoliosis affecting both her mother and her son, who over 4 years developed rapidly progressive scoliosis. The patient had a history of stable scoliosis since adolescence that worsened significantly at age 65, leading to low back pain and radiculopathy. Paraspinal muscle biopsy showed morphologic evidence of a mitochondrial myopathy. Diagnostic deficiencies of electron transport chain enzymes were not detected using standard bioassays, but mitochondrial immunofluorescence demonstrated many muscle fibers totally or partially deficient for complexes I, III, IV-I, and IV-IV. Massively parallel sequencing of paraspinal muscle mtDNA detected multiple deletions as well as a 40.9% heteroplasmic novel m.12293G > A (MT-TL2) variant, which changes a G:C pairing to an A:C mispairing in the anticodon stem of tRNA LeuCUN. Interestingly, these mitochondrial abnormalities were not detected in the blood of either the patient or her son, suggesting that the patient’s rapidly progressive late onset scoliosis was due to the acquired paraspinal mitochondrial myopathy; the cause of non-progressive scoliosis in the other two family members currently remains unexplained. Notably, this case illustrates that isolated mitochondrial myopathy can underlie rapidly-progressive adult-onset scoliosis and should be considered in the differential diagnosis of the primary axial myopathy.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-014-0137-3) contains supplementary material, which is available to authorized users.
Highlights
While adult scoliosis is a common disorder of the spine that often follows adolescent deformity, rapid progression of scoliosis with decompensation of posture occurs only rarely in the adult
A recent illustrative report demonstrated that heritable mitochondrial DNA mutations can cause an axial myopathy [8]: a familial late-onset axial myopathy due to mutation in the mitochondrial tRNA Phe gene was demonstrated in two elderly sisters with a history of encephalopathy and ataxia
We report a case of rapidly progressive adultonset scoliosis due to late-onset axial myopathy associated with multiple somatic mitochondrial DNA (mtDNA) abnormalities but without chronic myopathic features typically observed in primary axial myopathies
Summary
While adult scoliosis is a common disorder of the spine that often follows adolescent deformity, rapid progression of scoliosis with decompensation of posture occurs only rarely in the adult. Progressive adult-onset scoliosis is a debilitating and frequently painful condition that is poorly understood and typically considered idiopathic. While axial myopathies can be secondary to other neuromuscular disorders, in some cases they appear to arise de novo and are designated primary axial myopathies. While etiologically heterogeneous, this group of conditions is clinically characterized by progressive paraspinal muscle weakness, myogenic pattern on EMG, and normal to mildly elevated creatinine kinase (CK) levels. Mitochondrial changes (ragged red and cytochrome c oxidase (COX)-negative fibers) have been observed in primary axial myopathies [6,7], but are generally thought to represent non-specific age-related mitochondrial pathology. A recent illustrative report demonstrated that heritable mitochondrial DNA (mtDNA) mutations can cause an axial myopathy [8]: a familial late-onset axial myopathy due to mutation in the mitochondrial tRNA Phe gene was demonstrated in two elderly sisters with a history of encephalopathy and ataxia
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