The spinal muscular atrophies (SMA) affect lower motor neurons leading to important muscle atrophy and paralysis. Some cases of SMA affect mostly the lower limbs and are called autosomal dominant spinal muscular atrophy, lower extremity predominant (SMALED). So far, two genes have been identified to cause this phenotype, DYNC1H1 (SMALED1) and BICD2 (SMALED2). This pathology is rare, but patients exhibit classical features which should be recognised by physicians. We present two unrelated cases of SMALED2 with previously described c.320C>T BICD2 mutations. Our cases exhibit non-progressive weakness and atrophy of the lower limbs associated with contractures and unique muscle MRI findings suggestive of classical SMALED2. We also performed an extensive review of the literature to present the classical and atypical phenotypes of BICD2. Indeed, some features appear to be highly suggestive of the disease, including upper limb sparing, sparing of the adductors muscles on physical examination and MRI, congenital contractures and normal nerve conductions studies.

中文翻译：

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具有 BICD2 基因突变的 SMALED2：两例报告和经典表型描述

脊髓性肌萎缩症 (SMA) 会影响下运动神经元，导致重要的肌肉萎缩和瘫痪。一些 SMA 病例主要影响下肢，被称为常染色体显性脊髓性肌萎缩症，下肢为主（SMALED）。到目前为止，已经确定了两个基因导致这种表型，DYNC1H1 (SMALED1) 和 BICD2 (SMALED2)。这种病理是罕见的，但患者表现出应该被医生识别的经典特征。我们提出了两个不相关的 SMALED2 病例，其具有先前描述的 c.320C>T BICD2 突变。我们的病例表现出与挛缩相关的非进行性下肢无力和萎缩，以及提示经典 SMALED2 的独特肌肉 MRI 发现。我们还对文献进行了广泛的审查，以展示 BICD2 的经典和非典型表型。的确，