Objective: To identify the gene responsible for 14q32-linked dominant spinal muscular atrophy with lower extremity predominance (SMA-LED, OMIM 158600). Methods:Target exon capture and next generation sequencing was used to analyze the 73 genes in the 14q32 linkage interval in 3 SMA-LED family members. Candidate gene sequencing in additional dominant SMA families used PCR and pooled target capture methods. Patient fibroblasts were biochemically analyzed.Results: Regional exome sequencing of all candidate genes in the 14q32 interval in the original SMA-LED family identified only one missense mutation that segregated with disease state-a mutation in the tail domain of DYNC1H1 (I584L). Sequencing of DYNC1H1 in 32 additional probands with lower extremity predominant SMA found 2 additional heterozygous tail domain mutations (K671E and Y970C), confirming that multiple different mutations in the same domain can cause a similar phenotype. Biochemical analysis of dynein purified from patient-derived fibroblasts demonstrated that the I584L mutation dominantly disrupted dynein complex stability and function. Conclusions:We demonstrate that mutations in the tail domain of the heavy chain of cytoplasmic dynein (DYNC1H1) cause spinal muscular atrophy and provide experimental evidence that a human DYNC1H1 mutation disrupts dynein complex assembly and function. DYNC1H1 mutations were recently found in a family with Charcot-Marie-Tooth disease (type 2O) and in a child with mental retardation. Both of these phenotypes show partial overlap with the spinal muscular atrophy patients described here, indicating that dynein dysfunction is associated with a range of phenotypes in humans involving neuronal development and maintenance. Neurology ® 2012;78:1714-1720 GLOSSARY CMT ϭ Charcot-Marie-Tooth; gDNA ϭ genomic DNA; indels ϭ insertions/deletions; SDS-PAGE ϭ sodium dodecyl sulfate polyacrylamide gel electrophoresis; SMA ϭ spinal muscular atrophy; SMA-LED ϭ spinal muscular atrophy with lower extremity predominance; SNP ϭ single nucleotide polymorphism.Developmental and degenerative disorders affecting motor neurons or their axons produce a broad range of inherited human diseases, including spinal muscular atrophy (SMA), hereditary motor neuropathy, and amyotrophic lateral sclerosis. Many hypotheses regarding the pathophysiology of motor neuron loss (e.g., impaired axonal transport, aberrant protein aggregation, disrupted protein homeostasis, altered RNA metabolism 1,2 ) were first suggested by the identification of new genes producing hereditary motor neuron disease. To identify additional genes required for motor neuron survival, we studied a large pedigree with a rare form of dominantly inherited SMA with early childhood onset of weakness and disproportionate involvement of From the Department of Neurology

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Charcot-Marie-Tooth (CMT) disease is caused by mutations in several genes expressed in myelinating Schwann cells and the axons they ensheathe. Typical patients present with distally accentuated motor weakness, muscle wasting, and sensory loss leading to significant and progressive clinical morbidity and impaired quality of life. The wealth of recent information regarding genotype-phenotype correlations, recognition of disease heterogeneity, and newly characterized animal models provide exciting insights into the molecular disease-related pathogenetic and pathophysiologic mechanisms. These advances at the same time also represent a challenge for the diagnosis and management of these patients, with no presently available specific curative or disease modifying treatments. A better understanding of the pathogenesis of peripheral neuropathies is an invaluable tool in developing future supportive and curative therapies for patients with CMT disease that will improve their quality of life. In this review, we provide practical insights on current diagnostic and therapeutic modalities and suggest future diagnostic and therapeutic directions.

Treatment of patients with acquired (autoimmune) myasthenia gravis should rely on evidence-based therapeutic choices, taking into account the individual's needs according to disease severity (mild to severe), extent (ocular or generalized), comorbidities (including other autoimmune diseases, infections, thymoma, and pregnancy), age, iatrogenic factors (the risks and benefits of therapy), patient autonomy and quality of life, financial burden to the patient, and associated health care costs. Therapy is aimed at managing symptoms by improving neuromuscular junction transmission (cholinesterase inhibitors) and/or modifying the underlying immunopathogenetic cause of acquired myasthenia gravis via immunosuppression or immunomodulation. Myasthenic patients with operable thymoma should be referred for surgery and closely followed up for tumor recurrence. A concerted international effort is addressing treatment recommendations for thymectomy in myasthenic patients with no radiologic evidence of thymoma who are positive for circulating acetylcholine receptor antibodies. There is a lack of evidence-based treatment guidelines for both acute and long-term management of ocular myasthenia. Acute management of myasthenic crisis requires intensive monitoring of the patient and institution of an efficient and safe treatment such as plasma exchange. Patient education is essential to a comprehensive long-term treatment plan.