Ophthalmoplegia plus with morphological and chemical studies of cerebellar and muscle tissue

Megamitochondria formation - physiology and pathology

Mitochondria undergo structural changes simultaneously with their functional changes in both physiological and pathological conditions. These structural changes of mitochondria are classified into two categories: simple swelling and the formation of megamitochondria (MG). Data have been accumulated to indicate that free radicals play a crucial role in the mechanism of the MG formation induced by various experimental conditions which are apparently various. These include ethanol-, chloramphenicol- and hydrazine-induced MG formation. Involvement of free radicals in the mechanism of MG formation is showed by the fact that MG formation is successfully suppressed by free radical scavengers such as alpha-tocopherol, coenzyme Q(10), and 4-OH-TEMPO. Detailed mechanisms and pathophysiological meanings of MG formation still remain to be investigated. However, a body of evidence strongly suggests that enormous changes in physicochemical and biochemical properties of the mitochondrial membranes during MG formation take place and these changes are favorable for membrane fusion. A recent report showed that continous exposure of cells with MG to free radicals induces apoptosis, finding which suggests that MG formation is an adaptative process to unfavorable environments at the level of intracellular organelles. Mitochondria try to decrease intracellular reactive oxygen species (ROS) levels by decreasing the consume of oxygen via MG formation. If mitochondria succeed to suppress intracellular ROS levels, MG return to normal both structurally and functionally, and they restore the ability to actively synthesize ATP. If cells are additionally exposed to excess amounts of free radicals, MG become swollen, membrane potential of mitochondria (DeltaPsim) decreases, cytochrome c is released from mitochondria, leading to activation of caspases and apoptosis is induced.

Vascular involvement in benign infantile mitochondrial myopathy caused by reversible cytochrome c oxidase deficiency

A 1-month-old Japanese girl had profound generalized weakness, hypotonia, and severe lactic acidosis. The infant improved gradually: she held her head at 9 months, learned to walk by 15 months. At the first muscle biopsy at 11 weeks of age, the specimen was characterized by numerous ragged-red fibers and decreased enzyme activity on cytochrome c oxidase (COX) staining. Electron microscopic findings were characterized by the presence of excessive abnormal mitochondria not only in skeletal muscle fibers but also in blood vessels. Vascular abnormalities consisted of an increased number of enlarged mitochondria in endothelial and smooth muscle cells of small arteries. Biochemical analysis showed an isolated defect of COX activity, which was only 16% of the mean control level. At the second biopsy at 44 months of age, the COX activity had increased to normal in the entire specimen. On electron microscopy, the abnormal mitochondria present on the first biopsy specimen had disappeared both in muscle fibers and blood vessels; nearly all mitochondria were morphologically normal at the second biopsy. Now at 5 years of age she can run and does not show muscle weakness. We report reversibility of abnormal mitochondria with age not only in skeletal muscle fibers but also in blood vessels in a patient, who had reversible COX deficiency with a benign clinical course.

Focal cytochrome c oxidase deficiency in the brain and dorsal root ganglia in a case with mitochondrial encephalomyopathy (tRNA(Ile) 4269 mutation): histochemical, immunohistochemical, and ultrastructural study

This is the first report with histochemical and immunohistochemical techniques of an autopsy case with mitochondrial encephalomyopathy caused by the mitochondrial tRNA(Ile) (nt4269) A to G mutation showing focal cytochrome c oxidase (COX) deficiency of neuronal cells. The 18-year-old male patient had cardiomyopathy, hearing disability, mental retardation, and seizures. Muscle biopsy exhibited many ragged-red fibers and focal COX deficiency. A postmortem histochemical study on frozen sections of the cerebral cortex, cerebellum, brain stem, and dorsal root ganglia revealed a loss of COX activity in some neuronal cells. On immunohistochemical staining, COX was also defective in a mosaic pattern. Focal COX deficiency may cause variable neurological manifestations in mitochondrial encephalomyopathies.

Central and peripheral nervous system conduction in mitochondrial myopathy with chronic progressive external ophthalmoplegia

Involvement of the peripheral and central nervous systems in mitochondrial myopathy with chronic progressive external ophthalmoplegia (CPEO) has been demonstrated clinically and electrophysiologically. Systematic electrophysiological investigations of the peripheral and central nervous systems, particularly of cortico-spinal tract function, however, are not available. We studied peripheral and central nervous system involvement in 28 patients with histologically and biochemically proven mitochondrial CPEO by motor and sensory nerve conduction tests, by somatosensory, auditory and visual evoked potentials and, for the first time, by transcranial magnetic stimulation. Nervous system involvement could be demonstrated in 24 patients, affecting the peripheral and central nervous systems in 18 and 10 patients, respectively. Evidence of cortico-spinal tract involvement was found in 4 patients, which was clinically expected in only 2. Therefore, dysfunction of the cortico-spinal tract in mitochondrial CPEO may occur more frequently than so far assumed. Generally, electrophysiological tests serve as valuable supplements to clinical examination in patients with mitochondrial CPEO and may be especially helpful in therapeutic studies, i.e., coenzyme Q administration.

Defective brain energy metabolism shown by in vivo 31P MR spectroscopy in 28 patients with mitochondrial cytopathies

We studied brain energy metabolism by phosphorus magnetic resonance spectroscopy (31P MRS) in 28 patients with mitochondrial cytopathies, and 20 normal control subjects. Fourteen patients had myopathy alone, six had only mild brain symptoms, and eight showed different degrees of brain involvement. Brain 31P MRS showed a low phosphocreatine content in all patients, accompanied by a high inorganic phosphate in 14 of 28 patients. The average value of the Pi concentration in the patient group was significantly (p = 0.009) different from the control group. The cytosolic pH was normal. From these data were derived a high concentration of ADP (calculated from the creatine kinase equilibrium), a high percent value of V/Vmax for ATP biosynthesis, and a low phosphorylation potential, all features showing a derangement of brain energy metabolism, in all patients with mitochondrial cytopathies. 31P MRS proved to be sensitive enough to disclose a deficit of mitochondrial functionality not only in the affected patients, but also in those without clinically evident brain symptoms.

Endocrine dysfunction in Kearns-Sayre syndrome

Kearns-Sayre syndrome (KSS) is a form of mitochondrial myopathy in which specific clinical features, namely progressive external ophthalmoplegia, pigmentary retinal degeneration and cardiac conduction defects, occur. KSS has also been associated with a variety of endocrine and metabolic disorders, in particular short stature, gonadal failure, diabetes mellitus, thyroid disease, hyperaldosteronism, hypomagnesaemia, and bone, tooth and calcification abnormalities. A case is described exhibiting all of these features. A survey of the literature was conducted to determine the prevalence of these conditions among reported cases. Cases with hypoparathyroidism were considered separately to see if they constituted a distinct subgroup with multiple endocrine dysfunction. Short stature was common, being documented in 38% of cases. Gonadal dysfunction before or after puberty was also common (20% of cases) and affected both sexes equally. Diabetes mellitus was recorded in 13% of cases, half of which required insulin. Thyroid disease, hyperaldosteronism and hypomagnesaemia were uncommon but were probably not looked for in many cases. Bone or tooth abnormalities and calcification of the basal ganglia were found both in those with and without hypoparathyroidism. While endocrine and metabolic dysfunction was found more commonly in those with hypoparathyroidism this is likely to be due to increased recognition rather than increased prevalence. No evidence of an autoimmune polyendocrine syndrome including hypoparathyroidism was found.

Mitochondrial abnormalities in human sural nerves: fine structural evaluation of cases with mitochondrial myopathy, hereditary and non-hereditary neuropathies, and review of the literature

Fifteen cases of mitochondrial myopathy, three cases of hereditary motor and sensory neuropathy (HMSN) VI, and 280 cases of neuropathies of different etiologies were examined by electron microscopy for the presence of mitochondrial abnormalities in the sural nerve. Altered mitochondrial were found in most cases of mitochondrial myopathy, in all cases of HMSN VI, and in 25 cases out of the series of unselected neuropathies. The mitochondrial changes comprised enlargement with an amorphous matrix and distorted cristae, with hexagonal paracrystalline inclusions, and with prominent cristae containing oblique striations, and a variety of rare changes. Most mitochondrial abnormalities were found in Schwann cells. An increase of the number of mitochondria was noted in smooth muscle and endothelial cells of epineurial arterioles of two cases with mitochondrial encephalomyopathy. Neuropathy was present in all cases of mitochondrial myopathy according to morphometrical analysis. Whether neuropathy is caused directly by mitochondrial dysfunction or by other pathogenetic mechanisms remains to be determined.

Neuropathology in Kearns-Sayre syndrome

The neuropathological changes found at autopsy in a case of Kearns-Sayre syndrome are described. We have previously analyzed the respiratory chain function in isolated muscle mitochondria and also described a large deletion of muscle mitochondrial DNA (mtDNA) in this case. The neuropathological examination revealed prominent neuronal degeneration and gliosis of the basal ganglia and there were bilateral areas of softening and total loss of nerve cells in the lenticular nuclei. The pallidum and caudate nucleus disclosed accumulation of iron-containing pigment. The white matter in the cerebrum, brain stem and cerebellum showed widespread and focally accentuated spongy change due to splitting of myelin lamellae. It is suggested that deficiency of respiratory chain enzymes due to the mtDNA deletion is of pathogenetic importance in the development of the described changes.

Phosphorus magnetic resonance spectroscopy of patients with mitochondrial cytopathies demonstrates decreased levels of brain phosphocreatine

The hypothesis that brain mitochondria are directly affected in several phenotypes associated with disordered oxidative phosphorylation was tested using phosphorus 31 (31P) magnetic resonance spectroscopy. Abnormal phosphorylation potentials in skeletal muscle have been demonstrated by 31P magnetic resonance spectroscopy in patients with mitochondrial cytopathies (heritable disorders of oxidative phosphorylation), but abnormalities of phosphorylation potentials in other organs have not been documented. Several lines of evidence suggest that these mutations may affect mitochondria in nonmuscle tissue. In this study we found that phosphocreatine-to-ATP ratios in brain were significantly reduced and that calculated brain ADP concentrations, phosphorylation potentials, and percentage of maximal rate of ATP synthesis were significantly altered in the 5 patients examined. This study indicates a primary abnormality of mitochondrial function in the brain, even in the absence of clinically evident cerebral dysfunction.

Involvement of extraocular muscle in mitochondrial encephalomyopathy

We carried out a histological examination of the extraocular muscles (EOMs) in a case of myoclonus epilepsy associated with ragged-red fibers (MERRF) and two cases of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), which did not manifest external ophthalmoplegia clinically. By light microscopy, many granular and vesicular fibers were seen associated with endomysial fibrosis. Electron microscopy revealed that the fibers showed prominent accumulation of abnormal mitochondria, extensive loss of myofibrils, proliferation of free sarcoplasmic reticulum and an increased amount of lipid vacuoles. These changes were more pronounced in MELAS than in MERRF. Hirano bodies were often seen in the subsarcolemmal area of muscle fibers and also in the intramuscular myelinated nerve fibers and axon terminals. These findings suggest the presence of mitochondrial myopathy of the EOMs in cases of MELAS and MERRF.

Immunohistochemical demonstration of mitochondria in routinely processed tissue using a monoclonal antibody

We report results obtained using the monoclonal antibody M-II 68, which recognizes inner mitochondrial membrane in routinely processed (formalin-fixed and paraffin-embedded) tissue by light microscopic immunohistochemistry. In ten normal brains, the range of immunoreactivity in various cell types and locations was defined. The most intense staining was observed in Purkinje cells, in neurons of cranial nerve nuclei, pons and substantia nigra, as well as in choroid plexus epithelial cells. By comparison with this control group, one case of primary mitochondrial encephalomyopathy exhibited increased staining of endothelial and vascular smooth muscle cells, choroid plexus epithelial cells, and neurons of various locations. Scattered ragged-red fibres were heavily labelled in one case of mitochondrial myopathy, while ten muscles without mitochondriopathy were left unstained. Our method is able to detect accumulations of mitochondria and increases in mitochondrial cristae density. It could prove useful for differential diagnosis of routine biopsy material and for clarification of cell types involved in mitochondrial cytopathies.

Variation in retinal changes and muscle pathology in mitochondriopathies

A variety of retinal changes that have so far not been classified under mitochondriopathies can now be included in this group, since muscle biopsy has identified ragged-red fibers with pathological mitochondriae. The ophthalmological findings in our relatively large group of 12 patients with mitochondrial myopathies are compared with the spectrum of myopathic findings. No obvious correlation exists between the severity of the pathological retinal changes and the characteristic of the myopathic alterations. In addition to fine pigmentation and depigmentation, severe dystrophic changes of the retina, pigment epithelium, and the choroid were observed. In two patients with severe chorioretinal dystrophy the correlation with generalized mitochondriopathy was not suspected prior to muscle biopsy.

Further postmortem examination of a case of familial ataxia with cerebrospinal fluid abnormality: an electron microscopic study of the intracytoplasmic eosinophilic inclusion bodies in the central nervous system

As reported previously, the peculiar intracytoplasmic eosinophilic inclusion bodies (IEIBs) extensively appeared in the autopsied brain tissue from a 49-year-old man having familial ataxia with cerebrospinal fluid abnormality, and histochemically showed abundant proteins, but few lipids and carbohydrates. Ultrastructurally, many membrane-bound vacuoles derived from the distended cisterns of rough-surfaced endoplasmic reticulum (RER) appeared in the neurons. They were filled with fine granular, less dense materials. The IEIBs, shown as a homogeneous dense core, were found in some of the vacuoles. Similar vacuoles also appeared in astrocytes, oligodendrocytes, vascular pericytes, ependymal and choroidal epithelial cells. It is suggested that the vacuoles result from the accumulation of metabolic products in the distended RER cisterns of the cells in the central nervous system, presumably representing a genetically determined functional abnormality of the RER in protein synthesis and/or transport.

Vascular involvement in mitochondrial myopathy

Electron microscopic examination of muscle specimens taken at biopsy in 6 patients with complex I deficiency and 1 patient with an unknown primary chemical defect who had the clinical characteristics of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) revealed striking abnormalities in blood vessels in 5. Abnormalities consisted of an increased number of enlarged mitochondria with complicated cristae in the pericytes of capillaries, endothelial cells, and smooth muscle cells of the small arteries, including terminal arterioles and precapillary sphincters, predominantly in smooth muscle cells. On statistical analysis, the number of mitochondria and the ratio of mitochondrial area to the total area of the smooth muscle cells were increased approximately tenfold (p less than 0.001). Although stroke-like episodes were not present, similar mitochondrial abnormalities in blood vessels were found in 1 patient who had the encephalomyopathic form of complex IV deficiency and in 2 patients in whom the primary chemical defects could not be clearly defined. Such abnormalities in small arteries might be responsible for the occasional occurrence of transient cerebral ischemia causing stroke-like episodes and progressive mental deterioration.

Pathological findings of the sural nerve in mitochondrial encephalomyopathy

We examined the muscle and peripheral nerve of a 55-year-old woman with familial mitochondrial encephalomyopathy. In the gastrocnemius muscle, many ragged red fibers and mitochondria containing paracrystalline inclusions in those fibers were observed by light and electron microscopy, respectively. Histopathological studies of the sural nerve revealed a marked decrease in the number of large myelinated fibers. Electron microscopic studies showed an accumulation of glycogen particles and mitochondria containing abnormal, structurally obscure cristae in the Schwann cell cytoplasm. These results suggest that the cause of loss of the large myelinated fibers may be some disturbance of metabolism in the Schwann cells due to mitochondrial dysfunction.

Progressive cytochrome c oxidase deficiency in a case of Kearns-Sayre syndrome: morphological, immunological, and biochemical studies in muscle biopsies and autopsy tissues

We report biochemical, immunological, and morphological findings in a patient with fatal Kearns-Sayre syndrome. Histochemical and biochemical findings from muscle biopsy specimens obtained 7 years apart documented the disease's evolution from a mild mitochondrial disorder affecting a small proportion of muscle fibers to a severe disorder affecting a large proportion of muscle fibers. Cytochrome c oxidase activity in muscle declined profoundly as the disease progressed, although the level of enzyme protein was normal, as shown by immunochemical techniques. Other organs were severely affected by the disease. Examination of postmortem tissue showed spongiosis in the frontal cortex, diffuse loss of Purkinje cells in the cerebellum, liver steatosis, and heart fibrosis with mitochondrial abnormalities. Cytochrome c oxidase activity was only slightly reduced in these organs.

Involvement of choroid plexus in mitochondrial encephalomyopathy (MELAS)

Morphological study of the choroid plexuses of two patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) revealed an enormously increased number of mitochondria with structural abnormalities in almost all of the choroidal epithelial cells. The majority of the cells also showed loss of microvilli and collapsed or attenuated apical cytoplasmic processes with increased electron density and lysosome-like dense bodies. The blood vessels of the choroid plexus showed the features of mitochondrial angiopathy previously described in the pial arteries of the same patients. These findings are interpreted as the morphological expression of a primary biochemical defect of the mitochondrial function in the choroid plexus, and as the probable explanation for increased CSF lactate and pyruvate levels in this disease.

Histopathology of mitochondrial cytopathy and the Laurence-Moon-Biedl syndrome

Clinical and histopathological studies of two patients with distinctly different inherited juvenile retinal dystrophies indicate that the ocular defect in mitochondrial cytopathy involves the underlying pigment epithelium, whereas in the Laurence-Moon-Biedl syndrome the photoreceptor cells are primarily affected.

Peripheral neuropathy associated with mitochondrial myopathy

Twenty patients with mitochondrial myopathy were investigated for the presence of peripheral neuropathy. There were clinical features of a mild sensorimotor neuropathy in 5 patients (25%) and nerve conduction studies were abnormal in 10 patients (50%). Electrophysiological studies of the whole group showed significant impairment of motor and sensory conduction, compared with controls. Sural nerve biopsy and morphometric studies were performed on 4 patients with clinical neuropathy. There was a reduction in density of myelinated fibers and electron microscope features of axonal degeneration affecting myelinated and unmyelinated fibers. Abnormal mitochondria containing paracrystalline inclusions were seen in the Schwann cell cytoplasm of two nerves.

Ocular myopathies

Ocular myopathies are manifested by primary and progressive involvement of extraocular muscles. In most cases of involvement of extra-ocular muscles a biopsy from somatic muscles studied by histochemistry and electron microscopy permits to make the diagnosis of the underlying condition. The two main clinico-pathological types of ocular myopathies are the oculocraniosomatic syndrome (Kearns-Sayre syndrome) and oculopharyngeal muscular dystrophy. The oculocraniosomatic syndrome is a multisystemic disorder and its histopathological hallmark is the presence of ragged-red muscle fibres which contain aggregates of abnormal mitochondria, often with paracrystalline inclusions. In the oculopharyngeal muscular dystrophy are observed muscle fibres with rimmed vacuoles and intranuclear tubular filamentous inclusions about 8.5 nm in external diameter. The rimmed vacuoles may occur in other muscle diseases but the intranuclear inclusions appear to be specific for oculopharyngeal muscular dystrophy. Their nature is unknown.

Familial progressive external ophthalmoplegia with multisystem abnormalities: "new" features raising nosological problems

A 32-year-old female presented with progressive external ophthalmoplegia (PEO) and multisystem abnormalities, strikingly associated with myotonia and muscle hypertrophy. These two features were not found in her brother, who had a complex neuromuscular disorder complicating chronic PEO. In both subjects muscle biopsy revealed "ragged-red" fibres and myofibres containing glycogen granules, which were never bound by membranes. A severe demyelinating neuropathy was revealed by electrophysiological and morphological studies. Cranial CT scan showed extensive demyelination of the cerebral white matter. Genetic studies demonstrated that this familial syndrome is transmitted as an autosomal recessive trait.

Retinal pathology in the Kearns-Sayre syndrome

Examination of the retinal tissues obtained at necropsy from a 14-year-old boy with Kearns-Sayre syndrome showed marked photoreceptor and pigment epithelial cell loss in the retinal periphery and around the optic nerve head. Electron microscopy of surviving retinal pigment epithelial (RPE) cells indicated a loss of apical microvilli and basal infoldings. The RPE was unusually devoid of melanosomes and showed no evidence of phagocytosis of photoreceptor debris. The cytoplasm of the RPE contained numerous, often enlarged, mitochondria. These structural changes suggested that a breakdown in the energy dependent interrelationships between the RPE and the photoreceptor layer was responsible for the outer retinal degeneration. The finding of numerous macrophages in the subretinal space suggests a secondary inflammatory component in the retinal degeneration.

Abnormal mitochondria on a renal biopsy from a case of mitochondrial myopathy

Mitochondrial myopathy (MM) is reported in a 5-year-old girl with short stature, hypotonia, ptosis, retinal pigmentation, and Fanconi's syndrome. A muscle biopsy showed the characteristic features of MM, and a renal biopsy revealed abnormal mitochondria in tubular cells that were similar to those seen in the muscle. This is the first report of such findings in association with MM.

Oculoskeletal myopathy with abnormal mitochondria

A clinical, electrophysiological and pathological review of 14 patients having oculoskeletal myopathy with abnormal mitochondria was undertaken. These patients present with ophthalmoplegia, and mild skeletal muscle weakness. The clinical course is slowly progressive. Electromyographic examination shows myopathic changes. Serum enzymes are normal. The diagnosis is confirmed by skeletal muscle biopsy which shows abnormal mitochondria, including crystalloid inclusions on electron microscopy. These patients form a distinct clinical group in which the risk of sudden cardiac death is much less than it is in the Kearns-Sayre syndrome.

Dominant optic atrophy, deafness, ptosis, ophthalmoplegia, dystaxia, and myopathy. A new syndrome

Twenty-three members of a 96-member family exhibited an autosomal dominant disorder which has not previously been described. This disorder involves progressive optic atrophy, abnormal electroretinography without retinal pigment changes, and progressive sensorineural hearing loss usually evident in the first or second decade of life. In midlife, ptosis, ophthalmoplegia, dystaxia, and a nonspecific myopathy occur.

Congenital Leigh's disease: panencephalomyelopathy and peripheral neuropathy

A dystrophic newborn girl (38th week of gestation) presented as a floppy infant with relapsing episodes of lactic acidosis and progressive cerebral deterioration. She died after serious apnoea at the age of 8 weeks. Neuropathological examination demonstrated widespread changes of Leigh's subacute polioencephalomyelopathy affecting the cerebral cortex, basal ganglia, mesencephalon and spinal cord. In addition, there was severe leukoencephalopathy of the cerebral hemispheres with sudanophilic tissue degregation, advanced axonal loss and reactive astrocytic gliosis. There was marked demyelination of the sciatic nerves. Electron-microscopical examination of the hypertrophic heart revealed pathological mitochondria with tubular inclusions suggestive of primary mitochondrial cardiomyopathy. Similar mitochondrial changes were not detected in the CNS and PNS. The complex of neuropathological alterations in this case is nevertheless consistent with a congenital variant of Leigh's disease.

Electroencephalographic findings in patients with chronic progressive external ophthalmoplegia

A retrospective study of the electroencephalographic patterns in 26 adults with chronic progressive external ophthalmoplegia. 12 of them presented EEG anomalies, all slight and aspecific. Of the various parameters considered (age, age at onset, duration of disease, CT, CSF findings, abnormalities of muscle mitochondria) the only two that seem to correlate are altered EEG patterns and severity of mitochondrial anomalies in skeletal muscle tissue.

Immunological abnormalities in a family with progressive external ophthalmoplegia

The authors report the muscular and humoral immunological abnormalities found in a family with progressive external ophthalmoplegia (PEO) of the "pure" form. Serum circulating immune complexes as determined by the polyethylen glycol (PEG) test and double radial immunodiffusion (DRID) were positive for IgG in both cases studied and for IgM and Clq for the propositus. In the latter circulating auto-antibodies against smooth muscle were also present. Immunohistochemical studies on striated muscle of the propositus showed positive perivascular IgG and IgM staining and IgG in the sarcolemma basement membrane complex. It is suggested that in this family a genetically inherited abnormal immune response to the muscular blood vessel wall has induced vascular injury and ultimately chronic ischemic muscular damage. This is consistent with the view that PEO is a clinical syndrome, i.e. the expression of various defects affecting primarily or secondarily the energy metabolism of the muscular tissue.

Mitochondrial inheritance in a mitochondrially mediated disease

Mendelian inheritance involves the transmission to successive generations of DNA contained in genes in the nucleus, but DNA is also contained in mitochondria, where it is believed to be responsible for the encoding of certain mitochondrial enzymes. Since nearly all mitochondrial DNA is maternally transmitted, one might expect a nonmendelian pattern of inheritance in mitochondrial cytopathy, a syndrome in which there are abnormalities in mitochondrial structure and deficiencies in a variety of mitochondrial enzymes. We studied the pedigrees of 6 affected families whose members we had examined personally and of 24 families described in the literature. In 27 families, exclusively maternal transmission occurred; in 3 there was also paternal transmission in one generation. Altogether, 51 mothers but only 3 fathers had transmitted the condition. These results are consistent with mitochondrial transmission of mitochondrial cytopathy; the inheritance and enzyme defects of mitochondrial cytopathy can be considered in the light of recent evidence that subunits of respiratory-enzyme complexes are encoded solely by mitochondrial DNA. The occasional paternal transmission may be explained if certain enzyme subunits that are encoded by nuclear DNA are affected.

Focal deficiency of cytochrome-c-oxidase in skeletal muscle of patients with progressive external ophthalmoplegia. Cytochemical-fine-structural study

In skeletal muscle biopsies of 8 patients with progressive external ophthalmoplegia combined light and fine structural cytochemical studies of cytochrome-c-oxidase revealed the absence of the enzyme in single fibres with or without accumulation of abnormal mitochondria. However, some fibres showed abnormal mitochondria without any deficiency of the enzyme. In one case with only slight mitochondrial proliferation the existence of the enzyme defect was the most remarkable finding. The occurrence of the enzyme defect obviously does not depend on concomitant structural alterations of the chondriom. The results are consistent with an acquired mitochondrial injury leading to a gradual loss of enzyme activity either earlier (with or without a minimal reactive mitochondrial proliferation) or later (after a phase of mitochondrial proliferation) in the course of the disease. Focal lack of cytochrome-c-oxidase activity is apparently a constant feature of the syndrome; it therefore may be not only of pathogenetic but also of diagnostic importance and in this connection cytochemical-fine-structural demonstration of cytochrome-c-oxidase is a valuable method. In contrast to the biochemical approach it allows not only the detection but also the exact anatomical localization of single fibre defects.

"Mitochondrial myopathy" or mitochondrial disease? EEG, ERG, VEP studies in 13 children

Neurophysiological investigations (EEG, ERG, VEP) were carried out in 13 patients with proven "mitochondrial myopathy". There were nine girls and four boys. Varied abnormalities were seen in the EEGs of all cases, and in one patient unusual repetitive bursts of irregular slow waves and spikes were observed. The ERG was abnormal in five of the 12 cases tested, while the VEP (flash) was definitely abnormal in six out of these 12 cases. These neurophysiological findings suggest some involvement of both the brain and the visual system. It seem therefore appropriate that this condition be considered a "mitochondrial disease" affecting many systems rather than only muscles.

Mitochondrial cytopathy. A multisystem disorder with ragged red fibres on muscle biopsy

Thirteen children with abnormal mitochondria in muscle tissue, and a progressive neurological disorder that affected the cerebrum, cerebellum, extrapyramidal system, vestibular system, retina, upper motor neuron, lower motor neuron, and musculature, are reported. Other signs and symptoms were short stature, diabetes mellitus, cardiopathy, hypoplastic anaemia, glomerulopathy, and renal tubular dysfunction. These symptoms may occur singly or in various combinations and the manifestation may differ even within the same family. The most common clinical picture was that of "ophthalmoplegia plus'. Occurrence in relatives varied from isolated symptoms to the complete syndrome with "ragged red fibres' and is not inconsistent with an autosomal dominant mode of inheritance with variable expressivity. Theories for the pathophysiological basis of this syndrome are discussed and the literature reviewed.

Computed tomography in mitochondrial cytopathy

The clinical and computed tomographic (CT) findings in 11 proven cases of mitochondrial cytopathy (mitochondrial myopathy, Kearns Sayre syndrome, ophthalmoplegia plus) were studied. The CT changes included focal low density lesions in the basal ganglia and white matter and atrophy which could be slight or diffuse and severe. Calcification has been described in the basal ganglia, but did not occur in our series. Serial CT showed progression of the abnormalities. The differential diagnosis is discussed.

Kearns-Sayre syndrome. A case of the complete syndrome with encephalic leukodystrophy and calcification of basal ganglia

A case of a complete Kearns-Sayre syndrome, of early onset, associated with cerebral and cerebellar leukodystrophy and basal ganglia calcification is reported. The clinical, neurophysiological and morphological findings suggest multisystem involvement.

[An autosomal recessive syndrome with myopathy and central and peripheral nervous system involvement (author's transl)]

Three of 11 children, offspring of a consanguineous marriage, presented a progressive myopathy and seizures, associated with symptoms suggesting both central and peripheral nervous system involvement. The ultrastructural muscular lesions were not specific. The association of severe impairment of muscle tissue and of central nervous system is rare, being described in centronuclear myopathy, cerebromuscular dystrophy, Kearns-Sayre syndrome and in a few isolated cases. Clinically only these isolated observations and especially the Kearns-Sayre syndrome demonstrate analogies to our observations. These data lead us to the discussion of the specificity of ultrastructural lesions, especially mitochondrial abnormalities. Some authors consider these abnormalities to be the biochemical hallmark for ophthalmoplegia plus, whereas for others, especially Drachman, they are an inconstant and nonspecific finding, merely the consequence and not the cause of this disease. These observations argue for the relationship between muscular pathology and nervous system dysfunction.

Myoclonus epilepsy associated with ragged-red fibres (mitochondrial abnormalities ): disease entity or a syndrome? Light-and electron-microscopic studies of two cases and review of literature

A report is given of an association of dyssynergia cerebellaris myoclonica associated with Friedreich's ataxia and mitochondrial myopathy in 2 patients. They had suffered from gradually increasing bursts of myoclonus since the wage of 14 and childhood, respectively. The other striking clinical features included generalized convulsions, mental deterioration, intention tremor, ataxia, muscular atrophy and deformity of feet. Muscle biopsies revealed ragged-red fibres in both cases. On electron microscopy these fibres contained subsarcolemnal aggregations of abundant abnormal mitochondria with proliferation of inner membranes or paracrystalline inclusions. One of these patients showed elevated blood lactate and pyruvate with an increased lactate/pyruvate ration, apparently of primary origin. These 2 cases resemble those reported briefly by Tsairis et al. (1974). An association of dyssynergia cerebellaris myoclonica associated with Friedreich's ataxia and mitochondrial myopathy in these 2 patients is unlikely to be coincidental but may represent one nosological entity. This myoclonus epilepsy syndrome associated with ragged-red fibres is compared with other possibly related mitochondrial encephalomyopathies.

Familial mitochondrial myopathy with cataract

A 62-year-old female had severe progressive ophthalmoplegia associated with facial, pharyngeal and limb muscle involvement. When 40, she had undergone surgery for bilateral cataract present for about 20 years. Biopsies of skeletal muscles indicated myopathy; histochemistry and electron microscopy gave evidence of abnormal mitochondria in type I fibres. Bilateral cataract needing surgical treatment at 32 was the prominent symptom in her daughter, then with only mild facial weakness. Despite absence of ophthalmoplegia, similar pathological changes were observed in an inferior oblique muscle. The child of the former, a 10-year-old clinically healthy boy, had been surgically treated for a bilateral cataract at the age of 3. As indicated by a review of literature, cataract is not an exceptional occurrence in this particular type of ocular myopathy and therefore should be included within its multisystem associations. The same HLA haplotype (A2-B21) was found in the three patients.

Neuropathy and mitochondrial myopathy

It has been stated that peripheral neuropathy can be a feature of so-called ophthalmoplegia-plus syndrome, but to date only one case of hypertrophic neuropathy has been reported. This study is concerned with the clinical, electrophysiological, and pathological observations in a 37-year-old man with progressive external ophthalmoplegia and a ragged-red fiber myopathy associated with severe sensorimotor neuropathy. Histological and morphometric studies of the sural nerve revealed a marked loss of large myelinated fibers and an occasional degenerating axon. Residual fibers had disproportionately thin myelin sheaths in relation to axon calibers. In contrast to the muscle biopsy findings, no mitochondrial paracrystalline inclusions were observed in the nerve. However, the number of mitochondria per square micron of Schwann cell cytoplasm was elevated when compared with values obtained from normal subjects and a patient with a chronic neuropathy. These findings may indicate an alteration of mitochondrial function common to muscle fibers and Schwann cells which, in nerves, could lead to axon loss and abnormality of myelination.

Ophthalmoplegia plus. A multisystem disorder of unknown etiopathogenesis

Six cases of Ophthalmoplegia Plus (OP) have been studied: all the patients had palpebral ptosis, ophthalmoparesis and descending myopathy. Hypoacusis, cardiac conduction impairment, small stature, mental deficit and vestibulo-cerebellar dysfunction were present only in some cases. EMG showed a severe slowing of motor and sensory conduction velocity in one patient. Polyphasic and long duration MU action potentials, which are indicative of a neurogenic myopathy, were found in all cases. Every muscle biopsy showed many "ragged red fibers" which, in EM, appeared to contain abnormal mitochondria. According to the literature and our data, OP appears to be a multisystemic disorder with severe muscle mitochondrial abnormalities, but it is not certain whether it must be considered a syndrome with multiple etiological factors or a single nosological entity with different possibilities of clinical manifestations.

Autosomal dominant Kearns-Sayre syndrome

External ophthalmoplegia, retinal pigmentary degeneration, and heart block constitute the Kearns-Sayre syndrome. Skeletal muscle weakness, deafness, ataxia and endocrine disturbances also may occur. We examined 15 members in two generations of a family with autosomal dominant Kearns-Sayre syndrome. Seven had external ophthalmoplegia, six had electrocardiographic abnormalities, six had limb weakness nad six patients were normal. A deltoid muscle biopsy specimen from one patient contained typical "ragged-red fibers," abnormal lipid accumulation, and mitochondria increased in size and number, containing inclusions. The study demonstrated: (1) the marked variability in genetic expression; (2) the need to examine family members to discover asymptomatic patients and to establish an otherwise unrecognized hereditary pattern; and (3) the absence of specific and consistent biochemical abnormalities.

Extraocular muscle biopsy in chronic progressive external ophthalmoplegia

A quantitatives assessment of the pathological changes in extraocular muscle is presented in 8 patients with chronic progressive external ophthalmoplegia (CPEO). Serial cross-sections of extraocular muscle were stained with a battery of histochemical and immunohistochemical techniques and compared with 36 normal extraocular muscles and 1 muscle from a patient who had longstanding third nerve plasy with anomalous reinnervation. Several of the patients had a striking increase in the number of ragged-red fibers in extraocular muscle, particularly if frequent ragged-red fibers also were found on limb muscle biopsy. One patients demonstrated extrajunctional acetylcholine receptor (AChR) in a small percentage of fibers, although this finding was not present in the reinnervated muscle. Numerous darkly staining central regions were noted in the ocular muscle fibers of a patient with Stephens syndrome (CPEO, peripheral neuropathy, and cerebellar disease) and in the reinnervated muscle. A patient with myotubular myopathy had single central nuclei in both limb and ocular muscle. All patients demonstrated in their extraocular muscles variation in both the size and distribution of each of the three histochemical fiber types. Extraocular muscle biopsy proved to be a safe, reliable technique. As a similar quantitative analysis is applied to the study of further patients, a better understanding of the pathogenesis of CPEO should be possible.

Progressive extrinsic ophthalmoplegia with peripheral neuropathy and storage of muscle glycogen

A case of progressive extrinsic ophthalmoplegia associated with peripheral neuropathy and hypertriglyceridemia type IV is described. Motor and sensory conduction velocities of the spinal nerves were severely decreased, while the EMG of the facial muscles was more suggested of a myopathic disorder. Electron microscopic study of biopsies of biceps and peroneus brevis muscles disclosed many ragged red fibers, mainly type I, which contained typical abnormal mitochondria. Other fibers, all type II, contained increased amounts of glycogen between myofibrils or beneath the sarcolemmal membrane, but the mitochondria were normal. These fibers were more abundant in the peroneus brevis than in the biceps muscle. Nerve biopsy revealed marked loss of myelinated fibers, but neither mitochondrial changes nor glycogen storages were evident in Schwann's cells. Biochemical investigations confirmed the increased amount of glycogen in both muscle biopsies and revealed a decrease of guanilcyclase. Phosphorylase, phosphorylase b kinase, adenilcyclase, and carnitine concentrations were all normal. The pathogenesis of this syndrome is discussed and the relationship between mitochondrial abnormalities and glycogen accumulation in muscle tissue are considered.