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Abstract
The congenital myasthenic syndromes (CMS) are a heterogeneous group of disorders arising from genetic defects in presynaptic, synaptic, and postsynaptic proteins of the neuromuscular junction (NMJ) resulting in variable and characteristically fatigable muscle weakness affecting limb, ocular, bulbar, trunk, and respiratory muscles from early life. DOK7 mutation resulting in synaptic and postsynaptic CMS clinically presents with limb-girdle myasthenia with sparing of facial and EOM. They characteristically worsen with conventional treatment and show excellent response to salbutamol/ ephedrine. Here we present a case highlighting a varied presentation beginning in late childhood and its evolution to reveal its congenital nature and subsequent management with salbutamol.
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References
- Burke, G., Hiscock, A., Klein, A., Niks, E. H., Main, M., Manzur, A. Y., … Robb, S. (2013). Salbutamol benefits children with congenital myasthenic syndrome due to DOK7 mutations. Neuromuscular Disorders, 23(2), 170–175. https://doi.org/10.1016/j.nmd.2012.11.004
- Choi, K.-R., Berrera, M., Reischl, M., Strack, S., Albrizio, M., Roder, I. V., … Rudolf, R. (2012). Rapsyn mediates subsynaptic anchoring of PKA type I and stabilisation of acetylcholine receptor in vivo. Journal of Cell Science, 125(3), 714–723. https://doi.org/10.1242/jcs.092361
- Edgeworth, H. (1933). THE EFFECT OF EPHEDRINE IN THE TREATMENT OF MYASTHENIA GRAVIS: SECOND REPORT. JAMA: The Journal of the American Medical Association, 100(18), 1401. https://doi.org/10.1001/jama.1933.27420180001007
- Edgeworth, H. (1930). A REPORT OF PROGRESS ON THE USE OF EPHEDRINE IN A CASE OF MYASTHENIA GRAVIS. JAMA: The Journal of the American Medical Association, 94(15), 1136. https://doi.org/10.1001/jama.1930.27120410003009c
- Engel, A. G. (2007). The therapy of congenital myasthenic syndromes. Neurotherapeutics, 4(2), 252–257. https://doi.org/10.1016/j.nurt.2007.01.001
- Engel, A. G., Shen, X.-M., Selcen, D., & Sine, S. M. (2010). What Have We Learned from the Congenital Myasthenic Syndromes. Journal of Molecular Neuroscience, 40(1–2), 143–153. https://doi.org/10.1007/s12031-009-9229-0
- Jephson, C. G., Mills, N. A., Pitt, M. C., Beeson, D., Aloysius, A., Muntoni, F., … Bailey, C. M. (2010). Congenital stridor with feeding difficulty as a presenting symptom of Dok7 congenital myasthenic syndrome. International Journal of Pediatric Otorhinolaryngology, 74(9), 991–994. https://doi.org/10.1016/j.ijporl.2010.05.022
- Lashley, D., Palace, J., Jayawant, S., Robb, S., & Beeson, D. (2010). Ephedrine treatment in congenital myasthenic syndrome due to mutations in DOK7. Neurology, 74(19), 1517–1523. https://doi.org/10.1212/WNL.0b013e3181dd43bf
- Liewluck, T., Selcen, D., & Engel, A. G. (2011). Beneficial effects of albuterol in congenital endplate acetylcholinesterase deficiency and Dok-7 myasthenia. Muscle & Nerve, 44(5), 789–794. https://doi.org/10.1002/mus.22176
- Lorenzoni, P. J., Scola, R. H., Kay, C. S. K., Filla, L., Miranda, A. P. P., Pinheiro, J. M. R., … Werneck, L. C. (2013). Salbutamol therapy in congenital myasthenic syndrome due to DOK7 mutation. Journal of the Neurological Sciences, 331(1–2), 155–157. https://doi.org/10.1016/j.jns.2013.05.017
- Lorenzoni, P. J., Scola, R. H., Kamoi Kay, C. S., Lochmüller, H., & Werneck, L. C. (2013). Congenital myasthenic syndrome and minicore-like myopathy with DOK7 mutation. Muscle & Nerve, 48(1), 151–152. https://doi.org/10.1002/mus.23724
- Mahjneh, I., Lochmüller, H., Muntoni, F., & Abicht, A. (2013). DOK7 limb-girdle myasthenic syndrome mimicking congenital muscular dystrophy. Neuromuscular Disorders : NMD, 23(1), 36–42. https://doi.org/10.1016/j.nmd.2012.06.355
- Muller, J. S., Herczegfalvi, A., Vilchez, J. J., Colomer, J., Bachinski, L. L., Mihaylova, V., … Lochmuller, H. (2007). Phenotypical spectrum of DOK7 mutations in congenital myasthenic syndromes. Brain, 130(6), 1497–1506. https://doi.org/10.1093/brain/awm068
- Okada, K. (2006). The Muscle Protein Dok-7 Is Essential for Neuromuscular Synaptogenesis. Science, 312(5781), 1802–1805. https://doi.org/10.1126/science.1127142
- Palace, J., & Beeson, D. (2008). The congenital myasthenic syndromes. Journal of Neuroimmunology, 201–202, 2–5. https://doi.org/10.1016/j.jneuroim.2008.05.030
- Schara, U., Barisic, N., Deschauer, M., Lindberg, C., Straub, V., Strigl-Pill, N., … Lochmüller, H. (2009). Ephedrine therapy in eight patients with congenital myasthenic syndrome due to DOK7 mutations. Neuromuscular Disorders, 19(12), 828–832. https://doi.org/10.1016/j.nmd.2009.09.008
- Selcen, D., Milone, M., Shen, X.-M., Harper, C. M., Stans, A. A., Wieben, E. D., & Engel, A. G. (2008). Dok-7 myasthenia: Phenotypic and molecular genetic studies in 16 patients. Annals of Neurology, 64(1), 71–87. https://doi.org/10.1002/ana.21408
- Srour, M., Bolduc, V., Guergueltcheva, V., Lochmüller, H., Gendron, D., Shevell, M. I., … Brais, B. (2010). DOK7 mutations presenting as a proximal myopathy in French Canadians. Neuromuscular Disorders, 20(7), 453–457. https://doi.org/10.1016/j.nmd.2010.05.007
- Witting, N., & Vissing, J. (2014). Pharmacologic Treatment of Downstream of Tyrosine Kinase 7 Congenital Myasthenic Syndrome. JAMA Neurology, 71(3), 350. https://doi.org/10.1001/jamaneurol.2013.5590
- Yamanashi, Y., Higuch, O., & Beeson, D. (2008). Dok-7/MuSK signaling and a congenital myasthenic syndrome. Acta Myologica : Myopathies and Cardiomyopathies : Official Journal of the Mediterranean Society of Myology, 27, 25–29. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/19108574
References
Burke, G., Hiscock, A., Klein, A., Niks, E. H., Main, M., Manzur, A. Y., … Robb, S. (2013). Salbutamol benefits children with congenital myasthenic syndrome due to DOK7 mutations. Neuromuscular Disorders, 23(2), 170–175. https://doi.org/10.1016/j.nmd.2012.11.004
Choi, K.-R., Berrera, M., Reischl, M., Strack, S., Albrizio, M., Roder, I. V., … Rudolf, R. (2012). Rapsyn mediates subsynaptic anchoring of PKA type I and stabilisation of acetylcholine receptor in vivo. Journal of Cell Science, 125(3), 714–723. https://doi.org/10.1242/jcs.092361
Edgeworth, H. (1933). THE EFFECT OF EPHEDRINE IN THE TREATMENT OF MYASTHENIA GRAVIS: SECOND REPORT. JAMA: The Journal of the American Medical Association, 100(18), 1401. https://doi.org/10.1001/jama.1933.27420180001007
Edgeworth, H. (1930). A REPORT OF PROGRESS ON THE USE OF EPHEDRINE IN A CASE OF MYASTHENIA GRAVIS. JAMA: The Journal of the American Medical Association, 94(15), 1136. https://doi.org/10.1001/jama.1930.27120410003009c
Engel, A. G. (2007). The therapy of congenital myasthenic syndromes. Neurotherapeutics, 4(2), 252–257. https://doi.org/10.1016/j.nurt.2007.01.001
Engel, A. G., Shen, X.-M., Selcen, D., & Sine, S. M. (2010). What Have We Learned from the Congenital Myasthenic Syndromes. Journal of Molecular Neuroscience, 40(1–2), 143–153. https://doi.org/10.1007/s12031-009-9229-0
Jephson, C. G., Mills, N. A., Pitt, M. C., Beeson, D., Aloysius, A., Muntoni, F., … Bailey, C. M. (2010). Congenital stridor with feeding difficulty as a presenting symptom of Dok7 congenital myasthenic syndrome. International Journal of Pediatric Otorhinolaryngology, 74(9), 991–994. https://doi.org/10.1016/j.ijporl.2010.05.022
Lashley, D., Palace, J., Jayawant, S., Robb, S., & Beeson, D. (2010). Ephedrine treatment in congenital myasthenic syndrome due to mutations in DOK7. Neurology, 74(19), 1517–1523. https://doi.org/10.1212/WNL.0b013e3181dd43bf
Liewluck, T., Selcen, D., & Engel, A. G. (2011). Beneficial effects of albuterol in congenital endplate acetylcholinesterase deficiency and Dok-7 myasthenia. Muscle & Nerve, 44(5), 789–794. https://doi.org/10.1002/mus.22176
Lorenzoni, P. J., Scola, R. H., Kay, C. S. K., Filla, L., Miranda, A. P. P., Pinheiro, J. M. R., … Werneck, L. C. (2013). Salbutamol therapy in congenital myasthenic syndrome due to DOK7 mutation. Journal of the Neurological Sciences, 331(1–2), 155–157. https://doi.org/10.1016/j.jns.2013.05.017
Lorenzoni, P. J., Scola, R. H., Kamoi Kay, C. S., Lochmüller, H., & Werneck, L. C. (2013). Congenital myasthenic syndrome and minicore-like myopathy with DOK7 mutation. Muscle & Nerve, 48(1), 151–152. https://doi.org/10.1002/mus.23724
Mahjneh, I., Lochmüller, H., Muntoni, F., & Abicht, A. (2013). DOK7 limb-girdle myasthenic syndrome mimicking congenital muscular dystrophy. Neuromuscular Disorders : NMD, 23(1), 36–42. https://doi.org/10.1016/j.nmd.2012.06.355
Muller, J. S., Herczegfalvi, A., Vilchez, J. J., Colomer, J., Bachinski, L. L., Mihaylova, V., … Lochmuller, H. (2007). Phenotypical spectrum of DOK7 mutations in congenital myasthenic syndromes. Brain, 130(6), 1497–1506. https://doi.org/10.1093/brain/awm068
Okada, K. (2006). The Muscle Protein Dok-7 Is Essential for Neuromuscular Synaptogenesis. Science, 312(5781), 1802–1805. https://doi.org/10.1126/science.1127142
Palace, J., & Beeson, D. (2008). The congenital myasthenic syndromes. Journal of Neuroimmunology, 201–202, 2–5. https://doi.org/10.1016/j.jneuroim.2008.05.030
Schara, U., Barisic, N., Deschauer, M., Lindberg, C., Straub, V., Strigl-Pill, N., … Lochmüller, H. (2009). Ephedrine therapy in eight patients with congenital myasthenic syndrome due to DOK7 mutations. Neuromuscular Disorders, 19(12), 828–832. https://doi.org/10.1016/j.nmd.2009.09.008
Selcen, D., Milone, M., Shen, X.-M., Harper, C. M., Stans, A. A., Wieben, E. D., & Engel, A. G. (2008). Dok-7 myasthenia: Phenotypic and molecular genetic studies in 16 patients. Annals of Neurology, 64(1), 71–87. https://doi.org/10.1002/ana.21408
Srour, M., Bolduc, V., Guergueltcheva, V., Lochmüller, H., Gendron, D., Shevell, M. I., … Brais, B. (2010). DOK7 mutations presenting as a proximal myopathy in French Canadians. Neuromuscular Disorders, 20(7), 453–457. https://doi.org/10.1016/j.nmd.2010.05.007
Witting, N., & Vissing, J. (2014). Pharmacologic Treatment of Downstream of Tyrosine Kinase 7 Congenital Myasthenic Syndrome. JAMA Neurology, 71(3), 350. https://doi.org/10.1001/jamaneurol.2013.5590
Yamanashi, Y., Higuch, O., & Beeson, D. (2008). Dok-7/MuSK signaling and a congenital myasthenic syndrome. Acta Myologica : Myopathies and Cardiomyopathies : Official Journal of the Mediterranean Society of Myology, 27, 25–29. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/19108574