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| LETTER TO EDITOR |
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| Year : 2014 | Volume
: 62
| Issue : 3 | Page : 313-314 |
Familial Dok7 congenital myasthenic syndrome responsive to salbutamol
Boby Varkey Maramattom1, Rahul Patil1, Joe Thomas2
1 Department of Neurology, Lourdes Hospital, Kochi, Kerala, India
2 Department of Rheumatology, Lourdes Hospital, Kochi, Kerala, India
| Date of Submission | 25-Feb-2014 |
| Date of Decision | 26-Feb-2014 |
| Date of Acceptance | 02-Jun-2014 |
| Date of Web Publication | 18-Jul-2014 |
Correspondence Address:
Boby Varkey Maramattom
Department of Neurology, Lourdes Hospital, Kochi, Kerala
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0028-3886.136999
How to cite this article:
Maramattom BV, Patil R, Thomas J. Familial Dok7 congenital myasthenic syndrome responsive to salbutamol. Neurol India 2014;62:313-4 |
Sir,
A 40-year-old man of non-consanguineous parentage presented with progressive weakness. From early childhood, he had a clumsy gait followed by a waddling gait at the age of 26 years. Six months before the present admission, he developed progressive generalized weakness and mild dysphagia, and at presentation, he was wheelchair bound. He had fatigable ptosis, bifacial and jaw muscle weakness, neck and truncal weakness, and generalized muscle weakness (Grade 3-4/5). Mild wasting of the masseter, upper arm, shoulder girdle, and spinati muscles was noted [Figure 1]. Electrodiagnostic studies and low rate RNS revealed 58% decrement. Computed tomography of the thorax was normal. Acetylcholine receptor (AChR) antibodies, muscle receptor tyrosine kinase (MuSK) immunoglobulin G (IgG), and VGCC IgG were negative. Two of his sisters had a similar disease course. [Figure 2] He was started on pyridostigmine 60 mg 3 times a day with mild improvement, and his blood was sent for CMS genetic panel. After discharge, he again deteriorated and became chair bound within 2 months. CMS panel showed a homozygous mutation for DOK7 (c. 1124_1127dupTGCC p.Ala378Serfs*30) [Centogene AG, Germany]. He was started on oral salbutamol 2 mg 3 times a day. At 6 months follow-up, he had progressively improved and was ambulating independently. | Figure 1: Panel A shows wasting of the masseter muscles bilaterally. Panel B shows wasting of the shoulder girdle bilaterally
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Autosomal recessive DOK 7 gene ["downstream of kinase" 7] mutations produce a CMS with prominent proximal limb weakness. [1],[2] DOK7 CMS is a cytoplasmic protein interacting with the skeletal muscle receptor tyrosine kinase (MuSK) and is important in Agrin-independent MuSK activation during synapse development. [3] Features of DOK7-CMS include stridor, tongue wasting, limb-girdle weakness, and ptosis. [1] Genetic testing is necessary to confirm the diagnosis. Most patients with DOK7-CMS show a fleeting improvement with acetylcholinesterase inhibitor (AChEI) therapy. Treatment with salbutamol 2-4 mg tds produces gradual and sustained improvement possibly through postsynaptic β2-adrenoceptor binding, which improves stability and integrity of AChR. [4]
| » References | |  |
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| 2. | Palace J. DOK7 congenital myasthenic syndrome. Ann N Y Acad Sci 2012;1275:49-53.
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| 3. | Okada K, Inoue A, Okada M, Murata Y, Kakuta S, Jigami T, et al. The muscle protein Dok-7 is essential for neuromuscular synaptogenesis. Science 2006;312:1802-5.
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| 4. | Liewluck T, Selcen D, Engel AG. Beneficial effects of albuterol in congenital endplate acetylcholinesterase deficiency and Dok-7 myasthenia. Muscle Nerve 2011;44:789-94.
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[Figure 1], [Figure 2]
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