Novel BICD2 mutation in a Japanese family with autosomal dominant lower extremity-predominant spinal muscular atrophy-2

Introduction

The most common form of spinal muscular atrophy (SMA) is a recessive disorder caused by SMN1 mutations in 5q13, whereas the genetic etiologies of non-5q SMA are very heterogenous and largely remain to be elucidated. We present a father and son with atrophy and weakness of the lower leg muscles since infancy. Genetic studies in this family revealed a novel BICD2 mutation causing autosomal dominant lower extremity-predominant SMA type 2.

Long-term follow-up of a patient with autosomal dominant lower extremity-predominant spinal muscular atrophy-2 due to a BICD2 variant

IntroductionBicaudal D homolog 2 (BICD2) is a causative gene of autosomal-dominant lower extremity-predominant spinal muscular atrophy-2 (SMA-LED2). The severity of SMA-LED2 varies widely, ranging from cases in which patients are able to walk to cases in which severe joint contractures lead to respiratory failure. In this study, we report the long-term course of a case of SMA-LED2 in comparison with previous reports.Case reportThe patient was a 19-year-old woman. She had knee and hip dislocations with contractures, femoral fracture, and talipes calcaneovalgus since birth, and was diagnosed with arthrogryposis multiplex congenita. Intense respiratory support was not needed during the neonatal period. She had aspiration pneumonia repeatedly, necessitating NICU admission until 8 months of age. She achieved head control at 9 months of age and was able to sit at 2 years of age; however, she could not walk. Tube feeding was required until 3 years of age. At present, she can eat orally, move around with a wheelchair, and write words by herself. She needs non-invasive positive pressure ventilation during sleep because of a restrictive respiratory disorder during adolescence. Exome analysis identified a de novo heterozygous missense variant (c.2320G>A; p.Glu774Lys) in BICD2.ConclusionPatients with SMA-LED2 may have a relatively better prognosis in terms of social activities in comparison with the dysfunction in the neonatal period. Moreover, it is important to periodically evaluate respiratory function in patients with SMA-LED2 because respiratory dysfunction may occur during adolescence.     

Mutations of the LMNA gene can mimic autosomal dominant proximal spinal muscular atrophy

The molecular basis of autosomal dominant spinal muscular atrophy (AD-SMA) is largely unknown. Because the phenotypic spectrum of diseases caused by LMNA mutations is extremely broad and includes myopathies, neuropathies, and cardiomyopathies designated as class 1 laminopathies, we sequenced the LMNA gene in index patients with the clinical picture of proximal SMA, who had a family history suggestive of autosomal dominant inheritance. Among the 19 families investigated, two showed pathogenic mutations of the LMNA gene, resulting in the diagnosis of a class 1 laminopathy in about 10% of our series. We found one novel truncating mutation (c.1477C > T, Q493X) and one previously described missense mutation (c.1130G > T, R377H) in the LMNA gene of two unrelated patients with adult-onset proximal SMA followed by cardiac involvement 14 and 22 years after the onset of weakness. The pedigrees of both families revealed a high frequency of cardiac abnormalities or sudden deaths. Our findings extend the spectrum of laminopathies and are of relevance for genetic counseling and clinical care of families presenting with adult-onset proximal SMA. Particularly, if neurogenic atrophy is combined with a cardiac disease in a family, this should prompt LMNA mutation analysis.     

A severe female case of arthrogryposis multiplex congenita with brain atrophy,spastic quadriplegia and intellectual disability caused by ZC4H2 mutation

Arthrogryposis multiplex congenita (AMC) is characterized by heterogeneous multiple congenital contractures appearing at birth. Mutations in X-linked zinc-finger gene ZC4H2 were recently identified in some families and individuals with variable forms of AMC associated with dysmorphic signs, intellectual disability and spastic paresis. We present a non-consanguineous Japanese female presenting AMC with severe intellectual disability and spastic quadriplegia who also had progressive brain atrophy. Microarray-based comparative genomic hybridization identified 395?kb microdeletions at Xq11.2 which only included ZC4H2 gene. Previous reports showed that affected females have lesser symptoms and slight abnormality on brain MRI compared to male due to X-inactivation. Our case, however, showed severe manifestation than as ever reported as well as progressive diffuse brain atrophy, which implicated contribution of other genetic or environmental factors or extremely skewed X inactivation.     

A DYNC1H1 mutation causes a dominant spinal muscular atrophy with lower extremity predominance

Whole-exome sequencing of two affected sibs and their mother who showed a unique quadriceps-dominant form of neurogenic muscular atrophy disclosed a heterozygous DYNC1H1 mutation [p.H306R (c.917A>G)]. The identical mutation was recently reported in a pedigree with the axonal form of Charcot–Marie–Tooth disease. Three other missense mutations in DYNC1H1 were also identified in families with dominant spinal muscular atrophy with lower extremity predominance. Their clinical features were consistent with those of our family. Our study has demonstrated that the same DYNC1H1 mutation could cause spinal muscular atrophy as well as distal neuropathy, indicating pleotropic effects of the mutation.     

Cognitive functions in duchenne muscular dystrophy: A reappraisal and comparison with spinal muscular atrophy

In order to clarify cognitive functions in Duchenne muscular dystrophy (DMD), we performed a new controlled neuropsychological study. IQ (WISC-R), verbal skills (fluency, confrontation naming and syntax comprehension) and memory abilities (BEM) were studied in two matched groups; 24 DMD children and 17 spinal muscular atrophy (SMA) children aged 12–16 yr. A significant difference appeared between the DMD and SMA patients: only in the DMD group were there significant disabilities in certain specific functions and normal scores in others. Despite similar education, the DMD children more often had significantly greater learning disabilities. There were more DMD left-handers. Verbal IQ was significantly low whereas performance IQ was at a normal level. DMD children also performed poorly in reading tasks and in some memory functions such as story recall and verbal recognition. Specific cognitive disabilities in certain DMD children, not seen in SMA children, suggest a relationship with a DMD genetic disorder.     

Benign congenital muscular dystrophy with autosomal dominant heredity: problems of classification

Summary A family with autosomal dominant congenital muscular dystrophy affecting members of both sexes in three generations is described; a father and his two sons were studied. The onset of symptoms was in early childhood and progression, if any, was slow. The proximal limb muscles, the sternocleidomastoid and anterior tibial muscles were affected. One patient had torticollis and all had heel-cord shortening. An electrophysiological examination showed myopathy. There was no cardiomyopathy. Creatine kinase (CK) was elevated, and a histological study revealed a necrotizing myopathy with pronounced regeneration and formation of aberrant myofibrils (ringbinden) and fibrosis.     

Failure of lower motor neuron radial outgrowth precedes retrograde degeneration in a feline model of spinal muscular atrophy

Feline spinal muscular atrophy (SMA) is a fully penetrant, autosomal recessive lower motor neuron disease in domestic cats that clinically resembles human SMA Type III. A whole genome linkage scan identified a ～140-kb deletion that abrogates expression of LIX1, a novel SMA candidate gene of unknown function. To characterize the progression of feline SMA, we assessed pathological changes in muscle and spinal cord from 3 days of age to beyond onset of clinical signs. Electromyographic (EMG) analysis indicating denervation occurred between 10 and 12 weeks, with the first neurological signs occurring at the same time. Compound motor action potential (CMAP) amplitudes were significantly reduced in the soleus and extensor carpi radialis muscles at 8-11 weeks. Quadriceps femoris muscle fibers from affected cats appeared smaller at 10 weeks; by 12 weeks atrophic fibers were more prevalent than in age-matched controls. In affected cats, significant loss of L5 ventral root axons was observed at 12 weeks. By 21 weeks of age, affected cats had 40% fewer L5 motor axons than normal. There was no significant difference in total L5 soma number, even at 21 weeks; thus degeneration begins distal to the cell body and proceeds retrogradely. Morphometric analysis of L5 ventral roots and horns revealed that 4 weeks prior to axon loss, motor axons in affected cats failed to undergo radial enlargement, suggesting a role for the putative disease gene LIX1 in radial growth of axons.     

A follow-up study of 60 cases of chronic spinal muscular atrophy

60 cases of chronic spinal muscular atrophy (CSMA) were followed-up for a period varying from 5 to 40 years. The neuromuscular impairment was evaluated by Norris’ ALS score, both at the time of last examination and retrospectively at the time of diagnosis. Age at onset of symptoms was the most important factor in the progression of the neuromuscular damage. Monomelic or asymmetric location of symptoms at the time of diagnosis and duration of the disease were not significantly correlated to the worsening of ALS score.

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Sommario Sessanta casi di atrofia muscolare spinale cronica (CSMA) sono stati seguiti per un periodo compreso tra 5 e 40 anni. Per mezzo dell’ALS score di Norris è stato quantificato il danno neuromuscolare, sia al momento dell’ultima visita, sia, retrospettivamente, al momento della diagnosi. Il più importante fattore nella definizione della progressione del deficit è risultato essere l’età all’esordio dei sintomi. Non è stata evidenziata una relazione significativa tra una localizzazione monomelica o asimmetrica dei sintomi ed il peggioramento dell’ALS score.

     

A case of asymmetrical arthrogryposis--a clinical study and a preliminary report on the value of CT-scanning

Following the introduction of the conception that arthrogryposis is a symptom and not a clinical entity, a case of the very rare asymmetric form of neurogenic arthrogryposis is presented. The asymmetry of congenital contractures and weakness is associated with hemihypotrophy. The value of muscular CT-scanning prior to muscle biopsy is demonstrated. Muscular CT-scanning shows the extension of adipose tissue, which has replaced damaged muscles and thereby indicates the exact site for muscle biopsy. Since orthopaedic treatment in arthrogryposis can be unrewarding due to severe muscular degeneration, preoperative scanning may provide additional important information on muscular function and thus be of benefit for surgery. The advantage of muscular CT-scanning in other forms of arthrogryposis requires further determination. The differential diagnosis with Werdnig-Hoffmann disease is discussed.     

A natural history study of late onset spinal muscular atrophy types 3b and 4

Background   Spinal muscular atrophy (SMA) is caused by a homozygous deletion of the survival motor neuron (SMN)1 gene. The nearly identical SMN2 gene plays a disease modifying role. SMA is classified into four different subtypes based on age of onset and clinical course (SMA types 1–4). The natural history of early onset SMA types 1–3a has been studied extensively. Late onset SMA is rare and disease course has not been studied in detail. Objective   To perform a prospective study on the clinical course and the correlation with SMN2 copy numbers of late onset SMA. Methods   Patients fulfilling the diagnostic criteria for late onset SMA (types 3b and 4) were included in the study. At inclusion and follow-up, muscle strength, respiratory function, functional status and quality of life were assessed. SMN2 copy number was determined in all patients. Results   Twelve patients were identified and included. Six patients were siblings from one family, two patients were brothers from a second family and four patients were sporadic cases. All patients carried four copies of the SMN2 gene. Median age of disease onset was 22.2 years (10–37). Age of disease onset in patients from family one was lower as compared to the other patients. None of the outcome measures changed after a follow-up of 2.5 years. Five patients reported an increase in fatigue and muscle weakness. None of the patients showed symptoms of respiratory insufficiency. Conclusions   This study indicates that late onset SMA is not characterized by disease progression and that alternative or surrogate disease markers are required for the design of future trials. This study confirms the finding that SMN2 copy number is a SMA disease course modifier.     

An autopsy case of spinal muscular atrophy type III (Kugelberg‐Welander disease)

We report an autopsy case of a 67‐year‐old man clinicogenetically diagnosed as having spinal muscular atrophy (SMA) type III (Kugelberg‐Welander disease), showing slowly progressive muscle wasting and weakness of the extremities. His brother showed similar manifestations. Autopsy revealed neuronal loss and severe gliosis in the anterior horns of the spinal cord, a marked neurogenic change of skeletal muscles and mild degeneration of cardiomyocytes. Chromatolytic change was seen in the anterior horn, but not in the Clarke's and thalamic nuclei. The anterior spinal roots were atrophic, and there was loss of myelinated fibers with abundant glial bundles. In addition, degeneration was also observed in the posterior column and dentate nucleus. The pathological features were essentially similar to those of SMA I. Chronic change was prominent while acute change was mild in degree, corresponding to a very long clinical course.     

Is juvenile spinal muscular atrophy of the distal upper limbs due to cervical flexion myelopathy? A case report

A 22-year-old woman developed a slowly progressive symmetric weakness and muscular atrophy of distal upper limbs at the age of 17. Radiography during anteflexion and retroflexion showed a hypermobile cervical spine with a maximum at the C5/6 disc level. Cervical myelography and postmyelographic computed tomography (CT) of the lower cervical spine demonstrated a remarkable anterior shift of the dural sac during anteflexion resulting in anteroposterior compression of the lower spinal cord. Postmyelographic CT and magnetic resonance imaging (MRI) revealed atrophy of the lower spinal cord with bilateral cystic lesions. We suppose that repetitive straining and compression of the lower cervical cord during neck flexion of the hypermobile cervical spine caused selective necrosis of anterior horn cells with secondary cystic transformation. Mechanically induced flexion myelopathy should be considered in all young patients presenting with muscular atrophy of the distal upper limb. Functional CT myelography or dynamic MRI of the cervical spine are appropriate to demonstrate lower spinal cord compression during flexion.     

Perioperative complications of scoliosis surgery in patients with Duchenne muscular dystrophy and spinal muscular atrophy,focussing on wound healing disorders

Purpose: Patients with Duchenne muscular dystrophy (DMD) or spinal muscular atrophy (SMA), both neuromuscular diseases, sustain spinal scoliosis in the course of their disease. To reduce the concomitant major morbidity and to improve their quality of life, patients require surgical spine stabilization. This can lead to complications like respiratory, cardiac or neurological complications or wound healing disorders (WHD). To find out the different complexities and risk factors increasing the chance to develop a WHD, the inpatient database was analyzed. Methods: We performed a retrospective statistical study. Therefore, we analyzed the inpatient database of 180 patients (142 DMD and 38 SMA patients). The focus was on WHD. To figure out the risk factors leading to WHD, we conducted a logistic regression. Results: Cardiac complications occurred most frequently, followed by pulmonary complications and neurological lesions. Fifty-seven out of 180 patients developed a WHD. In 23 cases the WHD was aseptic, in the other 34 cases dermal organisms, Pseudomonas species and intestinal organisms were responsible. By means of the logistic regression, we were able to identify two more risk factors, in addition to diagnosis and gender, for developing a WHD in our patients: the year of surgery and the direction of pelvic tilt. Conclusions: Most common complications following scoliosis surgery are respiratory and cardiac complications. WHD is a severe complication that implies a prolonged therapy. Some risk factors for developing WHD could be identified in this analysis. Specifically, these were the date of surgery and the direction of pelvic tilt.     

Adolescent spinal muscular atrophy with calf hypertrophy and a deletion in the SMN gene

Spinal muscular atrophy (SMA) is generally associated with proximal weakness and muscle wasting. An X-linked variant with calf hypertrophy has been reported. We describe a young man with SMA type 4 with prominent calf hypertrophy in whom DNA analysis showed a homozygous deletion of exons 7 and 8 in the telomeric copy of the survival motor neuron gene. Calf hypertrophy may be seen uncommonly in autosomally inherited SMA.     

脊髓延髓肌萎缩症一家系患者的临床、电生理及分子遗传学特点

目的 通过分析2例脊髓延髓肌萎缩症 (SBMA)患者的临床表现并进行相关文献复习, 比较全面地认识SBMA的临床特点、发病机制、病理特点及诊断与鉴别诊断要点,提高SBMA诊断率.方法 对临床疑似SBMA的兄弟两人的临床和肌电图特点进行分析,并检测其雄激素受体(AR)基因第一外显子三核苷酸(CAG)串联重复情况.结合文献,总结SBMA的临床特点、病理基础和发生机制. 结果 2例患者均具有典型SBMA临床表现,AR基因CAG重复数均为49,可诊断为SBMA. 结论熟悉SBMA的临床特征,早期进行基因检测,可提高该病的诊断率.