Duchenne muscular dystrophy: plasma membrane loss initiates muscle cell necrosis unless it is repaired

Study of biopsies from 30 boys with Duchenne muscular dystrophy suggests that necrosis of muscle cells is initiated by loss of plasma membrane, followed, after a short interval, by Z disc lysis and mitochondrial changes to constitute the picture of fully developed necrosis. Empty basal lamina tubes containing collagen indicated that regeneration may fail to occur. The tubes form a basis for collagen deposition. Evidence suggests that small patches of membrane loss can be repaired, though a slice of superficial cytoplasm is lost, and a piece of detached basal lamina results. The markedly hypercontracted fibres seen did not show features of necrosis.

Pathological involvement of primary sensory neurons in Werdnig-Hoffmann disease

Seven patients with the typical clinical picture and muscle biopsy findings of classical Werdnig-Hoffmann disease showed Wallerian degeneration in their biopsied sural nerves. In dorsal root ganglia of one patient there were residual nodules and several chromatolytic neurons. By electron microscopy the changes of chromatolysis were confirmed and found to be consistent with an axonal reaction. Involvement of the primary sensory neuron is probably a regular pathologic feature of Werdnig-Hoffmann disease. The type of abnormality suggests in initial failure of the axon distal to the nerve roots.

Subacute skeletal myopathy induced by 2,4-dichlorophenoxyacetate in rats and guinea pigs

Rats and guinea pigs were injected with 2,4-dichlorophenoxyacetate (2,4-D) in amounts sufficient to keep them myotonic for over 12 hr daily. The biceps brachii muscles were studied by histochemistry, epoxy resin histology, and electron microscopy after one to five days. Changes observed include proliferation of the longitudinal component of the sarcoplasmic reticulum, production of new myofilaments on the periphery of cells and in nuclei, activation of satellite cells, accumulation of lipid droplets, myofibrillar damage with Z-disc streaming, necrosis, and regeneration. The action mehanisms of 2,4-D are not well understood. Some of the phenomena observed could be classified as proliferative and may be analogous to the auxin action of 2,4-D in plants. The production of intranuclear filaments is probably related to the diffusion of newly formed cytoplasmic proteins into nuclei.

Inclusion body myositis: a distinct variety of idiopathic inflammatory myopathy

We report six cases of inclusion body myositis (IBM), a distinct but infrequently recognized inflammatory disease of skeletal muscle. Clinically, IBM differs from dermatomyositis and polymyositis. It lacks features of collagen-vascular disease, has a relatively benign and protracted course, frequently involves distal muscles, is found mainly in males, and does not improve with corticosteroid treatment. Electronmicroscopic demonstration of abnormal filaments in muscle cells is necessary for definite diagnosis, but IBM may be suspected by the finding on cryostat sections of numerous hematoxylinophilic granules in "lined" vacuoles in muscle cells. These correspond to whorls of cytomembranes. Although in dermatomyositis the capillary network is partly destroyed, in IBM it is usually augmented. A viral etiology of IBM has been suggested but remains unproven.

The ultrastructural characteristics of the abnormal cytosomes in Batten-Kufs' disease

Patients with Batten-Kufs' disease may be divided into three groups by electronmicroscopy of their storage deposits. In the first group, those characterized by curvilinear profiles, there is a strong correlation with a particular clinical syndrome, the late infantile form of the disease. In the second group, characterized by finger-print profiles, there is great diversity as to age and type of presentation. This is paralleled by diversity in the deposits. To the third group belongs the infantile form of the disease, as well as rare patients with later onset. Pathological diagnosis can be reliably, conveniently and consistently made from biopsy of skin by electronmicroscopy, and usually from biopsy of skeletal muscle as well.

Juvenile dystonic lipidosis: an unusual form of neurovisceral storage disease

An unusual neurovisceral lipid storage disorder in two unrelated juvenile patients manifested itself by dystonia and involuntary movements, with facial grimacing, dysarthria, gait difficulty, and impaired manual dexterity. Supranuclear paresis of vertical gaze and splenomegaly were present. Absent were seizures, major intellectual deterioration, spasticity, or blindness. Histiocytes showed lysosomal storage of various phospholipids, cholesterol, neutral lipids, and autofluorescent material. Appendiceal neurons showed only an increse of phospholipids by histochemistry. Neuronal deposits differed ultrastructurally from these in histiocytes. Leukocyte sphingomyelinase activity was normal. The nosology of this disease and its relationship to so-called juvenile types of Niemann-Pick disease is discussed. The primary metabolic defect in these patients remains unknown.

Cardiac myxoma: a diagnostic challenge for the neurologist

Three patients with left atrial myxoma presented with prominent neurologic symptoms and signs (cerebrovascular disease and/or syncope) within the past year. Two patients died because antemortem diagnosis was late or missed. One patient was successfully treated. Cardiac myxoma produces protean clinical manifestations that do not always include cardiac signs and symptoms. Neurologists may be called on for diagnostic consultation in patients who will prove to have cardiac myxoma. Unexplained transient ischemic attacks, cerebral infarction, or syncope (with possible features of seizure activity) are common neurologic manifestations of this disease. Additionally, systemic symptoms, signs, and laboratory data suggestive of collagen vascular disease or vasculitis are also often present. Echocardiography is a dependable noninvasive procedure for a confirmation of diagnosis in suspected cases.

The childhood type of dermatomyositis

The childhood type fo dermatomyositis, which occurs in children and young adults, shows a specific constellation of pathologic changes in muscle. Capillary necrosis leads to capillary loss, generally starting on the periphery of muscle fascicles. Electron microscopy discloses undulating tubules in endothelial cells, lymphocytes, pericytes, and pseudosatellite cells. The muscle fiber damage is coextensive with capillary damage and probably results from progressive ischemia. The muscle cells, before atrophying, show mitochondrial elongation, Z disk streaming, focal myofibrillary loss, and occassionally selective thick filament loss. Muscle cell necrosis is rare and limited to infarctlike lesions. Inflammatory infiltrates, if present, occur only in connective tissue septa. The cause of the capillary damage has not been determined.

Experimental mitochondrial myopathy produced by in vivo uncoupling of oxidative phosphorylation

Two uncouplers of mitochondrial oxidative phosphorylation [2,4-dinitrophenol (DNP) and carbonylcyanide-m-chlorophenylhydrazone (CCCH)] were infused intra-arterially into a branch of the lower abdominal aorta of anesthetized rats over a 60-180 min period. An acute, severe, hypermetabolic state with systemic lactic acidosis and stiffness of the lower extremeities developed. In the plantaris muscles, by histochemistry, numerous "ragged red" fibers were present after the infusion. The "ragged red" areas presumably represented an absolute increase in mitochondrial mass in affected muscle fibers. By electron microscopy, linear inclusions were present in the intracristal space of many mitochondria. Simultaneous infusion of DNP and chloramphenicol, an inhibitor of mitochondrial protein synthesis, prevented the formation of ragged red fibers but not the intracristal inclusions. Infusion of relatively large amounts of oleic acid produced histochemical and electron-microscopic changes similar to those caused by the uncouplers. A possible pathogenesis of these reversible mitochondrial changes was discussed and their potential relevance to morphologic abnormalities of skeletal muscle mitochondria in human diseases was reviewed.

The motor unit profile in two experimental chronic myopathies

The motor unit profile of the rat soleus muscle has been studied in two types of experimentally induced chronic myopathy. Tetrabenazine administered for 6 weeks resulted in a moderate myopathy characterized by necrosis, regeneration, and hypertrophy of muscle fibers. This model was associated with a normal motor unit count. The twitch tension of the muscle remained normal, presumably because of hypertrophy of some of the soleus muscle fibers; however, tetanic tension was reduced. The twitch time to peak became very prolonged. Another myopathy, characterized only by regenerating muscle fibers, was produced 6 weeks after abdominal aortic ligation. In this model, the soleus motor unit count was also normal. Twitch and tetanic tensions were reduced, and the contraction time was prolonged. The findings are discussed in relation to the motor unit profile reported in human neuromuscular diseases.

The syndrome of systemic carnitine deficiency. Clinical, morphologic, biochemical, and pathophysiologic features

An 11-year old boy had had recurrent episodes of hepatic and cerebral dysfunction and underdeveloped musculature. Overt weakness developed at age 10. Lipid excess, especially in type I fibers, was found in muscle. Hypertrophied smooth endoplasmic reticulum and excessive microbodies were present in liver. Marked carnitine deficiency was shown in skeletal muscle, plasma, and liver. Ketogenesis was impaired on a high fat diet, but omega oxidation of fatty acids was enhanced. There was excessive glucose uptake and essentially no oxidation of labeled long-chain fatty acids by perfused forearm muscles in vivo. Oral replacement therapy restored plasma carnitine levels to normal, but not liver or muscle carnitine levels, and was accompanied by clinical improvement.

Lafora's disease: peroxisomal storage in skeletal muscle

A 17-year-old patient had myoclonic epilepsy caused by Lafora's disease. Biopsy showed polysaccharide accumulations within membrane-bound spaces in skeletal muscle cells. Some of the accumulations were morphologically similar to Lafora bodies as they have been seen in the brain. The histochemical reactions of these membrane-bound spaces suggested that they were peroxisomes. Polysaccharide accumulations also were demonstrated in hepatic cells, where they probably were located in the endoplasmic reticulum. Lafora's disease can be diagnosed by histochemical and electron microscopic study of skeletal muscle.