Clinical, morphological and genetic studies in a cohort of 21 patients with myofibrillar myopathy.

The term myofibrillar myopathies (MFM) refers to uncommon neuromuscular disorders that pathologically are characterized by myofibrillar degeneration and ectopic expression of several proteins. MFM are partly caused by mutations in genes that encode mainly Z-disk-related proteins (desmin, alphaB-crystallin, myotilin, ZASP, filamin C and BAG3). We reviewed clinical, light and electron microscopy, immunohistochemistry, immunoblotting and genetic findings of 21 patients with MFM (15 unrelated patients and three pairs of brothers) investigated at our neuromuscular center. MFM patients begin to show symptoms at any age, from juvenile to late adult life and present a different distribution of muscle weakness. Cardiac involvement and peripheral neuropathy are common. Typical histological features include focal areas with reduction/loss of ATPase and oxidative enzyme activity, and amorphous material (eosinophilic on hematoxylin and eosin and dark blue on Engel-Gomori trichrome) in these abnormal fiber areas. Electron microscopy shows disintegration of myofibrils starting from the Z-disk and accumulation of granular and filamentous material among the myofilaments. Immunohistochemical studies demonstrate focal accumulation of desmin, alphaB-crystallin and myotilin in abnormal muscle fibers while immunoblot analysis does not highlight differences in the expression of these proteins also including ZASP protein. Therefore, unlike immunoblot, immunohistochemistry together with light and electron microscopy is a useful diagnostic tool in MFM. Finally three of our 21 patients have missense mutations in the desmin gene, two brothers carry missense mutations in the gene encoding myotilin, one has a missense mutation in alphaB-crystallin, and none harbour pathogenic variations in the genes encoding ZASP and BAG3.

Protein Expression of Canine and Feline Muscular Dystrophies.

Muscular dystrophies in dogs and cats represent a heterogeneous group of inherited, sometimes congenital, but infrequently diagnosed, progressive neuromuscular disorders. A correct identification and characterization of canine and feline muscular dystrophies could increase diagnostic and treatment strategies for veterinary neurologists and could identify useful animal models for the study of human dystrophies. However, in dogs and cats, diagnosis of muscular dystrophies is challenging due to a nonspecific clinical phenotype and pathological lesions, thus is most likely underestimated. We performed immunofluorescence and Western blot techniques using a wide panel of antibodies against proteins involved in human dystrophies (dystrophin mid-rod and carboxyterminal domain, α, ß, γ, and δ-sarcoglycan, α-dystroglycan, caveolin-3, emerin, merosin, dysferlin, calpain-3, spectrin epitopes), on 9 canine and 3 feline muscle biopsies characterized by myopathic changes. Dystrophin deficiency was detected in 3 dogs and 2 novel canine muscular dystrophies have been identified, characterized by deficiency of caveolin-3 and calpain-3, respectively. In 2 cats, deficiency of ß-SG and carboxyterminal domain of dystrophin in all muscle fibers has been detected. Performing immunofluorescence and Western blot analyses with a wider panel of antibodies allowed a correct identification of muscular dystrophies in dogs and cats and provides a direction for subsequent targeted genetic testing.

Facioscapulohumeral muscular dystrophy: epidemiological and molecular study in a north-east Italian population sample.

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant disease associated with a partial deletion on chromosome 4q35. Few relevant investigations have been reported on its epidemiology and were essentially based on clinical diagnosis, having been performed before recognition of the molecular mutation. We report an epidemiological survey on FSHD patients, in which the diagnosis was obtained by combined clinical and molecular evaluation. The survey concerned the north-east Italian province of Padova, an area of 871,190 inhabitants (1 January 2004). We identified 40 patients affected by FSHD based on clinical diagnosis. In 33 of them, the EcoRI fragment size in the 4q35 region ranged from 14 to 35 kb. Four other patients belonging to the same family harbored a 38-kb fragment. In these four cases, the relationship between the borderline deletion with the mild FSHD phenotype was corroborated by additional haplotype reconstruction and segregation analysis. Interestingly, the same mild facial-sparing clinical pattern was apparent only in one other patient with an EcoRI fragment of 32 kb, suggesting that this unusual FSHD phenotype may be due to very small 4q35 deletions. On the whole, estimating a prevalence rate of 44 x 10(-6), our survey confirmed FSHD as one of the most frequent neuromuscular disorders in Western populations.

Facioscapulohumeral muscular dystrophy: hearing loss and other atypical features of patients with large 4q35 deletions.

BACKGROUND AND PURPOSE: Patients affected by facioscapulohumeral muscular dystrophy (FSHD) with unusual large 4q35 deletions tend to present atypical features in early childhood. We explored the clinical presentation of patients with a very short 4q35 fragment (10-13 kb) focusing on hearing loss, a still debated FSHD extra-muscular manifestation. PATIENTS AND METHODS: We evaluated six cases with EcoRI 4q35 fragment size ranging from 10 to 13 kb. Assessment of hearing function was carried out by otoscopy, audiometry and auditory-evoked brainstem responses (ABR). Patient data were compared with those of 28 similar subjects reported in the literature. RESULTS: Sensorineural hearing loss was found in four patients, who presented infantile-onset dystrophic phenotype. Hearing loss was associated with mental retardation in three of them and with epilepsy in two. Auditory ability of the other two cases was mildly impaired. If findings related to 28 similar cases reported to date are also considered, auditory impairment appears evident in 68% of these subjects. CONCLUSIONS: Hearing loss represents a characteristic feature of FSHD patients with a large 4q35 deletion. Moreover, when considering only cases with 10-11 kb, it appears to be associated with early-onset dystrophic phenotype, with mental retardation (92%) and possibly with epilepsy (58%).

Eyelid ptosis from sympathetic nerve dysfunction mistaken as myopathy: a simple test to identify this condition.

Acquired isolated unilateral or bilateral blepharoptosis has many aetiologies. When the pupils are normal, a myasthenic syndrome or myopathy has to be ruled out. If the tests for myasthenia gravis are negative, the next step is to perform a muscle biopsy to establish a diagnosis. Muscle examination may show a mitochondrial disorder, non-specific abnormalities or be quite normal. We identified three patients, who had previously undergone various investigations, including a muscle biopsy, whose lid ptosis disappeared using eye drops containing naphazoline nitrate, a sympathomimetic drug, thus suggesting partial Horner's syndrome. We emphasise the usefulness of this simple and cheap test before performing more traumatic and expensive investigations.

Characterization of sarcoplasmic reticulum Ca(2+) ATPase pumps in muscle of patients with myotonic dystrophy and with hypothyroid myopathy.

Sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase (SERCA) pumps play the major role in lowering cytoplasmic calcium concentration in skeletal muscle by catalyzing the ATP-dependent transport of Ca(2+) from the cytosol to the lumen of the sarcoplasmic reticulum (SR). Although SERCA abnormalities have been hypothesized to contribute to the dysregulation of intracellular Ca(2+) homeostasis and signaling in muscle of patients with myotonic dystrophy (DM) and hypothyroid myopathy, the characterization of SERCA pumps remains elusive and their impairment is still unclear. We assessed the activity of SR Ca(2+)-ATPase, expression levels and fiber distribution of SERCA1 and SERCA2, and oligomerization of SERCA1 protein in muscle of patients with DM type 1 and 2, and with hypothyroid myopathy. Our data provide evidence that SR Ca(2+) ATPase activity, protein levels and muscle fiber distribution of total SERCA1 and SERCA2, and SERCA1 oligomerization pattern are similar in patients with both DM1 and DM2, hypothyroid myopathy and in control subjects. We prove that SERCA1b, the neonatal isoform of SERCA1, is expressed at protein level in muscle of patients with DM2 and, in lower amount, of patients with DM1. Our present study demonstrates that SERCA function is not altered in muscle of patients with DM and with hypothyroid myopathy.

Increased expression of the normal cellular isoform of prion protein in inclusion-body myositis, inflammatory myopathies and denervation atrophy.

The cellular isoform of the prion protein (PrPc) is a glycosylphosphatidylinositol-anchored glycoprotein, normally expressed in neural and non-neural tissues, including skeletal muscle. In transmissible spongiform encephalopathies, or prion diseases, PrPc, which is soluble in nondenaturing detergent and sensitive to proteinase K (PK)-treatment, represents the molecular substrate for the production of a detergent-insoluble and PK-resistant isoform, termed PrP(Sc). In human prion diseases, PrP(Sc) accumulation occurs only in brain tissues, with the exception of new variant Creutzfeldt-Jakob disease, where PrP(Sc) is also detected in lymphoid tissues. Increased amounts of prion protein expression and deposition have been described in pathological muscle fibers of two human muscle disorders, called sporadic inclusion-body myositis (s-IBM) and hereditary inclusion-body myopathy, but it is unknown whether accumulated prion protein reflects normal PrPc or PrP(Sc). We investigated the biochemical characteristics of prion protein in normal human muscle, s-IBM, other inflammatory myopathies and denervation atrophy. We report that 1) both the glycoform profile and size of the normal muscle PrPc are different from those of human brain PrPc; 2) in addition to s-IBM, increased PrPc expression is seen in polymyositis, dermatomyositis and neurogenic muscle atrophy, but PrPc glycoforms are unchanged; 3) only the normal PrPc isoform, and not PrP(Sc), is detected in s-IBM. The present results exclude that s-IBM is a prion disease.

Implicit redundant-targets effect in visual extinction.

Patients with left visual extinction as a result of unilateral right hemisphere damage were tested on a redundant-targets effect paradigm (RTE). LED-generated brief flashes were lateralized either to the left or to the right visual hemifield or presented bilaterally. Subjects were asked to press a key as fast as possible following either unilateral or bilateral stimuli and immediately afterwards to report on the number of stimuli presented. As previously found in normal subjects, bilateral stimuli were responded to faster than unilateral ones, and this was evidence of a RTE. The main thrust of this study was that extinction patients showed a RTE not only for correctly perceived bilateral stimuli but also in trials in which they extinguished the stimulus on the field contralateral to the lesion. This result is compatible with a preserved processing of the extinguished input at least up to the stage at which it may interact with the input from the normal side to yield a speeded motor response. Interestingly, the implicit redundancy gain of extinction patients was found to fit a coactivation (i.e. neural) rather than a probabilistic model.

Polyglucosan body myopathy: a new case.

We report a 51-yr-old woman with late-onset progressive weakness affecting proximal limb muscles. Muscle biopsy revealed a vacuolar myopathy with accumulation of amylopectin-like polysaccharide resembling the polyglucosan found in type IV glycogenosis and adult-onset polyglucosan body disease. A biochemical study ruled out specific enzymatic defects known to cause storage of this abnormal material. Our case confirms the existence of a 'polyglucosan body myopathy' as a distinct clinicopathological entity in which the biochemical defect is unknown.

A new mutation in the mitochondrial tRNA(Ala) gene in a patient with ophthalmoplegia and dysphagia.

We describe a new mutation in the tRNA(Ala) gene, a T-->C transition at nucleotide position 5628, in a 62-year-old woman with late onset chronic progressive external ophthalmoplegia, dysphagia and mild proximal myopathy. The mutation is heteroplasmic and disrupts a highly conserved A-U base pair within the anticodon stem of the tRNA(Ala). Cytochrome c oxidase-negative fibers harbor a significantly higher level of mutated mtDNA than cytochrome c oxidase-positive fibers. This is the first mutation in the tRNA(Ala) gene which satisfies accepted criteria for pathogenicity.

T-cell anti-apoptotic mechanisms in inflammatory myopathies.

Recent studies have shown an up-regulation of the Fas/Fas ligand system in inflammatory myopathies. In myositis, however, the major Fas-mediated cytotoxicity which activates caspases bypasses apoptosis. We therefore evaluated the expression of proteins promoting cell survival, such as bcl-2, bcl-x(l) and cyclin-dependent kinase inhibitors, on muscle biopsies from 14 patients with polymyositis, dermatomyositis, inclusion body myositis and HIV-associated myositis. Our data demonstrate that inflammatory cells are immunoreactive for bcl-x(l), p16 and p57, three apoptosis-preventing proteins. Hence, we assume that these proteins might protect T cells from apoptotic nuclear changes. Our results could explain the non-self-limiting nature of inflammatory myopathies.

Hypokalemic periodic paralysis. A single fiber electromyographic study.

The neurophysiological findings obtained with standard electromyography (EMG) and single fiber EMG (SFEMG) in a case of hypokalemic periodic paralysis (HoPP) are reported. During the period between paralytic attacks the only abnormalities consisted of scanty fibrillation potentials and, with SFEMG, a fiber density increase. In the first stage of an induced paralytic attack the most striking feature was decrease in fiber density, slight increase in jitter with several blocks. These results indicate a failure of the membrane surface to propagate an action potential. In some fibers the block is likely to be permanent, thus explaining the decrease in fiber density. The jitter increase is due to a slight abnormality at the synaptic site or to a variation in the propagation velocity of the muscle fiber.

Minipolymyoclonus in congenital nemaline myopathy: a nonspecific clinical marker of neurogenic dysfunction.

The authors report a seven-month-old boy with severe hypotonia, poor spontaneous movements, breathing difficulties and recurrent respiratory infections, dysmorphisms and a peculiar movement disorder: minipolymyoclonus (MPM), previously reported only in spinal muscular atrophies. MPM is characterized by nonrhythmic myoclonic jerks associated with a rhythmic tremor of the extended fingers polygraphically detected. A muscle biopsy showed pathological changes typical of congenital nemaline myopathy (CNM). The relationship between MPM and CNM may be explained on the presumptive basis of the "neurogenic" nature of this congenital myopathy or by the non-specificity of this clinical sign.

Critically ill patients: immunological evidence of inflammation in muscle biopsy.

AIM AND METHOD: To verify whether muscle necrosis in critically ill patients could be due to an inflammatory process, we tested muscle biopsies from five intensive care patients with different inflammation-specific immunocytochemical markers (antibodies anti-class I major histocompatibility complex products (class I MHCP or HLA I), membrane attack complex (MAC), T lymphocytes helper-inducer (CD4), cytotoxic (CD8) and pan-B-lymphocytes). RESULTS: In three patients muscle biopsy showed class I MHCP positivity on the surface membrane of several groups of fibres, mainly perifascicular, and scattered microvascular deposits of MAC. In the other two patients muscle biopsy did not show class I MHCP and MAC positivity. CONCLUSION: Our results suggest that inflammation may be a component of muscle damage in some critically ill patients.