Infantile progressive muscular atrophy; value of muscle biopsy in the diagnosis of and its differentiation from muscular dystrophy.
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We studied the development of language in 3-4-year-old children with type II spinal muscular atrophy (SMA) (10 boys and two girls), aged 36-47 months (mean age 39.83+/-4.68 months) and compared our findings to a control group of 26 healthy children (mean age 40.00+/-4.43 months, 22 boys and four girls). We carried out a lexicogrammatical analysis of the data and we observed significant differences in the "vocabulary", "nouns", "verbs", "words" and "adverbs" variables between the children with SMA and the controls. Three- to four-year-old children suffering from type II spinal muscular atrophy, an autosomal genetic disease causing severe physical handicap (motor, functional, respiratory), presented a higher level of lexical and semantic development than the controls, demonstrating the precocity of development of morphosyntax in these children.
We analysed the reading abilities and processing of 21 children with Duchenne muscular dystrophy (DMD), 11 matched children suffering from spinal muscular atrophy (SMA) and 42 children receiving normal education. The principal result observed was that the DMD children exhibited a reading age which was significantly lower than the SMA children compared with their chronological age. These learning disabilities were not related to a deficit in non-verbal performance intelligence, but psycholinguistic evaluation showed a deficit in verbal intelligence, especially in the Similarities and Arithmetic WISC-R subtests, in phonological abilities, oral word repetition, and in digit span score. The results for the DMD children were heterogeneous, and ranged from normal to greater or lesser involvement. In an attempt to clarify the nature of this reading impairment in DMD children, the three groups (DMD, SMA, and normal control children) were tested by reading aloud a list of single words and non-words. The DMD children were significantly impaired in reading non-words, suggesting reading disability similar to dysphonetic dyslexia, the most frequent subtype of developmental dyslexia. These results are discussed in the light of psychometric data available for our DMD population and in the light of previous studies. The practical consequences of diagnosis on rehabilitation are very important. The precise description of the cognitive deficits seen in DMD is of value for future clinical and genetic studies.
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Alteration of correct splicing patterns by disruption of an exonic splicing enhancer may be a frequent mechanism by which point mutations cause genetic diseases. Spinal muscular atrophy results from the lack of functional survival of motor neuron 1 gene (SMN1), even though all affected individuals carry a nearly identical, normal SMN2 gene. SMN2 is only partially active because a translationally silent, single-nucleotide difference in exon 7 causes exon skipping. Using ESE motif-prediction tools, mutational analysis and in vivo and in vitro splicing assays, we show that this single-nucleotide change occurs within a heptamer motif of an exonic splicing enhancer, which in SMN1 is recognized directly by SF2/ASF. The abrogation of the SF2/ASF-dependent ESE is the basis for inefficient inclusion of exon 7 in SMN2, resulting in the spinal muscular atrophy phenotype.
We report a 37-year-old female with spinal muscular atrophy (SMA) type III and central nervous system (CNS) involvement. She showed gait disturbance at the age of 12 years, and difficulty of squatting at the age of 19. On examination at the age of 22, she had proximal muscle weakness and atrophy, fasciculation, normal sensory system and elevated creatine kinase in the serum. She was diagnosed as having SMA type III based on clinical, electrophysiological, and muscle biopsy findings. She suffered from subacute necrotizing lymphadenitis at the age of 23 and from epilepsy at the age of 33. Magnetic resonance imaging showed atrophy of parahippocampal gyrus with right side predominance. Single photon emission computed tomography (SPECT) using I123-IMP showed decreased accumulations of I123-IMP in the temporal lobes with left side predominance. Electroencephalogram showed theta wave without epileptic burst. SMA gene analysis revealed deletion of exon 7 and 8 in survival motor neuron (SMN) gene. A few patients with SMA and CNS involvement have been reported without genetic diagnosis. This is the first report of genetically confirmed SMA patient with CNS involvement. SMN gene is distributed not only in spinal cord but also in brain. The CNS involvement detected in this patient may be related to the loss of SMN gene function, although coincidental association of SMA and the CNS abnormalities is still considered in this atypical case.
Proximal spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder characterized by degeneration of anterior horn cells in the spinal cord leading to weakness and wasting of voluntary muscles. Here we present the molecular analysis of both SMA candidate genes, the survival motor neuron gene (SMN; exons 7 and 8) and the neuronal apoptosis inhibitory protein gene (NAIP; exons 5, 6 and 13), in 195 patients and 348 parents of SMA families mainly of German origin. The SMN gene is homozygously deleted for both exons 7 and 8 or exon 7 only in 96% of type I SMA, 94% of type II SMA and 82% of type III SMA as well as in 0.3% of SMA parents. The NAIP gene is homozygously deleted in 46% of type I SMA, 17% of type II SMA, 7% of type III SMA and 2% of SMA parents. The frequencies of deletions in patients for both genes, SMN and NAIP, correspond to those for the NAIP gene only. SMA patients of this series who did not show deletions were clinically indistinguishable from deleted patients. In addition to one unaffected mother of a type II SMA patient, we found homozygous deletions of the SMN gene exons 7 and 8 in six further unaffected individuals, all sibs of type II and III patients. These belonged to four families with affected and unaffected sibs who showed identical haplotypes for all SMA flanking markers; therefore, we had regarded these families as chromosome 5 unlinked. All seven unaffected individuals in whom we detected SMA deletions do not show any signs of muscle weakness and are physically inconspicuous. The largest divergence between age at onset of an affected subject and the present age of unaffected deleted sibs is four decades now. The occurrence of SMN deletions in unaffected individuals suggests that other genes or mechanisms may be necessary to produce the SMA phenotype.
Three patients from two families had an unusual phenotypical variant of late-onset hexosaminidase-A deficiency. The clinical picture was dominated by spinal motor neuron involvement mimicking juvenile-onset spinal muscular atrophy. Atypical features included prominent muscle cramps, postural and action tremor, recurrent psychosis, incoordination, corticospinal and corticobulbar involvement, and dysarthria. The presence of these atypical features in patients whose lower motor neuron involvement would otherwise be consistent with juvenile-onset spinal muscular atrophy should raise the suspicion of the presence of hexosaminidase-A deficiency and GM2 gangliosidosis that can be proved by appropriate enzyme assays.
This paper describes a genetic study of the chronic spinal muscular atrophies of late infancy and early childhood in Algeria. There were 50 index patients occurring in 44 kindreds and fourteen secondary cases. Genetic and nosological studies indicated that 52% of the patients constitute a genetically homogeneous subgroup with an age of onset between 3 and 24 months and an autosomal recessive mode of transmission. They also indicated that a large subgroup of index patients (48%) had a late age of onset, between 3 and 14 years. Such a large number of late presenting cases has not been reported in previous series. The majority of these cases are probably due to an autosomal recessive gene. A small proportion may represent new dominant mutations or nongenetic phenocopies. A possible sex influence on disease manifestations is discussed. A trend toward later male onset has been noted, and the degree of disability is more marked in males at or after the age of 10. Finally, some empirical risks for use in genetic counselling are presented.
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Chronic childhood-onset spinal muscular atrophy (SMA) is, after Duchenne muscular dystrophy, the most common neuromuscular disorder in childhood. Recent linkage analyses have mapped this disease to 5q12-5q14. We show that chronic SMA (Types II and III) is tightly linked to the marker locus D5S39 (Zmax = 5.47 at theta = 0.02) in eight French Canadian families. In contrast to previously published results, we do not observe close linkage between chronic SMA and D5S6 (Zmax = 0.34 at theta = 0.18) or D5S78 (Zmax = 0.25 at theta = 0.21). Last, we present a family that appears to be discordant for this localization but may represent the first example of an incompletely penetrant individual.
Pregnancy imposes a load on the respiratory system that is usually easily assumed because of alterations in the thoracoabdominal architecture. It is presumed that the respiratory mechanical disadvantage of severe kyphoscoliosis and the muscle weakness of spinal muscular atrophy impede these adaptations sufficiently to preclude a successful gestation. We report the case of a successful pregnancy in a woman with spinal muscular atrophy, severe uncorrected scoliosis, and the lowest spirometric values reported in the literature without the use of ventilatory support. This patient demonstrates that women with severe kyphoscoliosis and a profound ventilatory limitation can carry a successful pregnancy well into the third trimester without requiring full ventilatory support.
The appearance of tremors in patients with childhood, chronic spinal muscular atrophy has been known for years. We were struck by the presence of a "muscle tremor" artifact in the ECGs of all our patients with this diagnosis. This observation has not been noted previously. The consistency of this finding in patients with this disease is the basis for this report.
Spinal and bulbar muscular atrophy (SBMA) is an adult-onset motoneuron disease caused by a CAG-repeat expansion in the androgen receptor (AR) gene and for which no curative therapy exists. However, since recent research may provide opportunities for medical treatment, information concerning the natural history of SBMA would be beneficial in planning future clinical trials. We investigated the natural course of SBMA as assessed by nine activities of daily living (ADL) milestones in 223 Japanese SBMA patients (mean age at data collection = 55.2 years; range = 30-87 years) followed from 1 to 20 years. All the patients were diagnosed by genetic analysis. Hand tremor was an early event that was noticed at a median age of 33 years. Muscular weakness occurred predominantly in the lower limbs, and was noticed at a median age of 44 years, followed by the requirement of a handrail to ascend stairs at 49, dysarthria at 50, dysphagia at 54, use of a cane at 59 and a wheelchair at 61 years. Twenty-one of the patients developed pneumonia at a median age of 62 and 15 of them died at a median age of 65 years. The most common cause of death in these cases was pneumonia and respiratory failure. The ages at onset of each ADL milestone were strongly correlated with the length of CAG repeats in the AR gene. However CAG-repeat length did not correlate with the time intervals between each ADL milestone, suggesting that although the onset age of each ADL milestone depends on the CAG-repeat length in the AR gene, the rate of disease progression does not. The levels of serum testosterone, an important triggering factor for polyglutamine-mediated motoneuron degeneration, were maintained at relatively high levels even at advanced ages. These results provide beneficial information for future clinical therapeutic trials, although further detailed prospective studies are also needed.
OBJECTIVE: To describe the clinical findings of patients with spinal muscular atrophy (SMA) with survival motor neuron (SMN) gene deletion. METHOD: Descriptive study of SMA cases confirmed with the deletion of the SMN gene. Frequency determination of positive clinical and laboratory revised diagnostic criteria. RESULTS: All of the 22 included patients had symmetrical muscle weakness, which was diffuse in those with onset of symptoms up to 6 months of age (75 %), and either proximal or predominant in lower limbs in the remaining group (67 %). Fasciculations and atrophy were both frequent findings (82 %). Laboratory tests findings were variable, with a positivity of 57 % for electrophysiology and of 58 % for muscle biopsy. CONCLUSION: The presence of a deletion in the SMN gene can help to confirm this diagnosis in unclear presentations.
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The survival motor neurons (smn) gene in mice is essential for embryonic viability. In humans, mutation of the telomeric copy of the SMN1 gene causes spinal muscular atrophy, an autosomal recessive disease. Here we report that the SMN protein interacts with the zinc-finger protein ZPR1 and that these proteins colocalize in small subnuclear structures, including gems and Cajal bodies. SMN and ZPR1 redistribute from the cytoplasm to the nucleus in response to serum. This process is disrupted in cells from patients with Werdnig-Hoffman syndrome (spinal muscular atrophy type I) that have SMN1 mutations. Similarly, decreased ZPR1 expression prevents SMN localization to nuclear bodies. Our data show that ZPR1 is required for the localization of SMN in nuclear bodies.