{"id":6445,"date":"2018-06-01T05:41:10","date_gmt":"2018-06-01T05:41:10","guid":{"rendered":"https:\/\/hksnmd.org\/spinal-muscular-atrophy\/"},"modified":"2023-05-15T14:41:27","modified_gmt":"2023-05-15T06:41:27","slug":"spinal-muscular-atrophy","status":"publish","type":"page","link":"https:\/\/hksnmd.org\/en\/neuromuscular-diseases\/spinal-muscular-atrophy\/","title":{"rendered":"Spinal Muscular Atrophy"},"content":{"rendered":"\t\t
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What is 5q Spinal Muscular Atrophy (5q-SMA)?<\/h4>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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\n\t\t\t\t\t\t\t\t\tSpinal Muscular atrophy, also known as SMA, affects 1\/6000 to 1\/10,000 live births1<\/sup> and is a leading genetic cause of death in infant2<\/sup>. It encompasses a group of inherited neuromuscular disorders which affect the nerve cells, called motor neurons, in the anterior horn cells of the spinal cord that control voluntary muscle movement such as crawling, walking, raising arms, holding objects with hands , moving head and neck around, breathing, and swallowing. The most common form of SMA is caused by loss or mutation of the survival motor neuron 1 gene (SMN1<\/em>) on chromosome 5. \u00a0This predominated form is called 5q-SMA, which accounts for about 95% of SMA cases3<\/sup>. The SMN1 gene<\/em> is responsible for producing an important protein called survival motor neuron (SMN) protein, which are required for the proper functioning of motor neuron. As the SMN1<\/em> gene does not make enough SMN protein, the motor neurons break down, preventing the muscles from receiving proper signals from the brain. This in turn leads to progressive atrophy of the skeletal muscles. There are other rare forms of SMA which are not caused by SMN1<\/em> gene mutation (such as SMA with Respiratory Distress, distal SMA, and etc.). These forms vary considerably in severity and are broadly called non 5q-SMA.\u00a0 Unless specify, the use of the word \u201cSMA\u201d in the content below refers to 5q-SMA only<\/strong>.\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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What are the types and symptoms of 5q Spinal Muscular Atrophy1,4<\/sup>?<\/h4>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Each SMA children has different severity of weakness generally correlates with the age of onset. Weakness is greater proximally (muscles closer to the body such as shoulder, hips and upper back muscles) than distally (muscles not close to the body such as hands and feet) and generally greater in the legs than the arms. There are often loss of reflexes. In severe cases of SMA, the muscles responsible for breathing and swallowing may also be severely affected. SMA children have normal cognition and sensation.<\/p>\n

SMA is commonly classified into 4 main clinical types (from Type I through Type IV) according to the age of onset and\/or highest level of motor development milestone attained (Table 1). Milestones can include the ability to sit, stand, or walk. These \u201ctypes\u201d are not rigid categories, there is a wide spectrum of severity and considerable variability in the rate of progression within each type.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Table 1 \u2013 Clinical classification of SMA<\/strong><\/p>\n\n\n\n\n\n\n\n
Type<\/strong><\/td>\nOnset age<\/strong><\/td>\nLife Span<\/strong><\/td>\nHighest Motor Ability<\/strong><\/td>\n<\/tr>\n
Type I (severe)<\/td>\nPrenatal to first 6 months of infancy<\/td>\n< 2 yrs<\/td>\nNever sit independently<\/td>\n<\/tr>\n
Type II (intermediate)<\/td>\n6-18 months<\/td>\n> 2 yrs<\/td>\nSits alone. Never walk independently<\/td>\n<\/tr>\n
Type III (mild)<\/td>\n18 months to 17 yrs old<\/td>\nAdult<\/td>\nWalk independently<\/td>\n<\/tr>\n
Type IV (adult)<\/td>\n> 18 yrs old<\/td>\nNormal<\/td>\nWalk independently<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Table 1 \u2013 Clinical classification of SMA <\/strong><\/p>\n\n\n\n\n\n\n\n
Type<\/strong><\/td>\nOnset age<\/strong><\/td>\nLife Span<\/strong><\/td>\nHighest Motor Ability<\/strong><\/td>\n<\/tr>\n
Type I (severe)<\/td>\nPrenatal to first 6 months of infancy<\/td>\n< 2 yrs<\/td>\nNever sit independently<\/td>\n<\/tr>\n
Type II (intermediate)<\/td>\n6-18 months<\/td>\n> 2 yrs<\/td>\nSits alone. Never walk independently<\/td>\n<\/tr>\n
Type III (mild)<\/td>\n18 months to 17 yrs old<\/td>\nAdult<\/td>\nWalk independently<\/td>\n<\/tr>\n
Type IV (adult)<\/td>\n> 18 yrs old<\/td>\nNormal<\/td>\nWalk independently<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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