A Likely Pathogenic variant in the KBTBD13 Gene: A Case Series of Three Patients with Nemaline Myopathy Type 6.

IF 3.2 4区 医学 Q2 CLINICAL NEUROLOGY
Esmee S B van Kleef, Karlijn Bouman, Joery P F Molenaar, Josine M de Winter, Floor A M Duijkers, Filip Eftimov, Corien C Verschuuren-Bemelmans, Tineke van der Laan, Benno Küsters, Edoardo Malfatti, Erik-Jan Kamsteeg, Baziel G M van Engelen, Coen A C Ottenheijm, Jonne Doorduin, Nicol C Voermans
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Abstract

Background: Nemaline myopathy type 6 (NEM6) or KBTBD13-related congenital myopathy is the most prevalent type of nemaline myopathy in the Netherlands and is characterised by mild childhood-onset axial, proximal and distal muscle weakness with prominent neck flexor weakness combined with slowness of movements. The most prevalent variant in the Netherlands is the c.1222C > T p.(Arg408Cys) variant in the KBTBD13 gene, also called the Dutch founder variant.

Objective: To provide a comprehensive clinical and functional characterisation of three patients to assess the pathogenicity of a newly identified variant in the KBTBD13 gene.

Results: We present three cases (Patient 1: female, 76 years old; Patient 2: male, 63 years old; and his brother Patient 3: male, 61 years old) with a c.1222C > A p.(Arg408Ser) variant in the KBTBD13 gene. Patient 1 was also included previously in a histopathological study on NEM6. Symptoms of muscle weakness started in childhood and progressed to impaired functional abilities in adulthood. All three patients reported slowness of movements. On examination, they have mild axial, proximal and distal muscle weakness. None of the patients exhibited cardiac abnormalities. Spirometry in two patients showed a restrictive lung pattern. Muscle ultrasound showed symmetrically increased echogenicity indicating fatty replacement and fibrosis in a subset of muscles and histopathological analyses revealed nemaline rods and cores. Slower muscle relaxation kinetics with in vivo functional tests was observed. This was confirmed by in vitro functional tests showing impaired relaxation kinetics in isolated muscle fibres. We found a genealogic link between patient 1, and patient 2 and 3 nine generations earlier.

Conclusions: The c.1222C > A p.(Arg408Ser) variant in the KBTBD13 gene is a likely pathogenic variant causing NEM6.

KBTBD13 基因中的一个可能致病的变异体:三例内膜肌病 6 型患者的病例系列。
背景:6型神经性肌病(NEM6)或KBTBD13相关先天性肌病是荷兰最常见的神经性肌病类型,其特征是儿童期发病的轻度轴向、近端和远端肌无力,颈屈肌无力突出,伴有动作迟缓。荷兰最常见的变异是 KBTBD13 基因中的 c.1222C > T p.(Arg408Cys)变异,也称为荷兰始祖变异:目的:对三名患者的临床和功能特征进行全面分析,以评估新发现的 KBTBD13 基因变异体的致病性:结果:我们发现三例患者(患者1:女,76岁;患者2:男,63岁;患者3:男,61岁)的KBTBD13基因中存在c.1222C > A p.(Arg408Ser)变异。患者 1 之前还参加过一项关于 NEM6 的组织病理学研究。肌无力症状始于儿童时期,成年后逐渐发展为功能受损。三位患者均表示行动迟缓。经检查,他们有轻微的轴向、近端和远端肌无力。三位患者均无心脏异常。两名患者的肺活量检查显示肺部呈限制型。肌肉超声波显示对称性回声增高,表明部分肌肉中存在脂肪替代和纤维化,组织病理学分析显示有神经纤维棒和核心。在体内功能测试中观察到肌肉松弛动力学减慢。体外功能测试也证实了这一点,显示离体肌纤维的松弛动力学受损。我们发现患者 1 与九代之前的患者 2 和 3 之间存在谱系联系:结论:KBTBD13 基因中的 c.1222C > A p.(Arg408Ser) 变异很可能是导致 NEM6 的致病变异。
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来源期刊
Journal of neuromuscular diseases
Journal of neuromuscular diseases Medicine-Neurology (clinical)
CiteScore
5.10
自引率
6.10%
发文量
102
期刊介绍: The Journal of Neuromuscular Diseases aims to facilitate progress in understanding the molecular genetics/correlates, pathogenesis, pharmacology, diagnosis and treatment of acquired and genetic neuromuscular diseases (including muscular dystrophy, myasthenia gravis, spinal muscular atrophy, neuropathies, myopathies, myotonias and myositis). The journal publishes research reports, reviews, short communications, letters-to-the-editor, and will consider research that has negative findings. The journal is dedicated to providing an open forum for original research in basic science, translational and clinical research that will improve our fundamental understanding and lead to effective treatments of neuromuscular diseases.
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