The 4 Types of Spinal Muscular Atrophy

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by Marta Ribeiro |

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Spinal muscular atrophy (SMA) is a debilitating, severe disease that affects mainly children, shutting down their body, their muscles and organs but in varying ways according to type. There are four SMA types: type 1, 2, 3, and 4.

To help you understand a little more about the different types of SMA, here’s a list:



clinical trial infants

Also known as Werdnig-Hoffmann disease, type 1 is the most severe and common type of SMA. It is commonly diagnosed in a child’s first six months of life. More than 60% of spinal muscular atrophy cases are the often fatal type 1.

Read our article “Promising Results of SMA Therapy in Mice Targets ‘Backup Gene’ SMN2.”



Is usually diagnosed in a child between six months and two years old. Those who live with this type of SMA can typically sit by themselves but they are unable to walk and will require a wheelchair.

Find out how researchers have developed new mice models for SMA types 2 and 3.


03/Junio/2016 Madrid, Arganda del Rey. Álvaro prueba el primer exoesqueleto diseñado para niños en el Centro de Automática y Robótica, CAT, del CSIC. © JOAN COSTA / CSIC

Also known as Kugelberg-Welander disease, type 3 is normally diagnosed between 18 months and three years old. Patients with this type can initially walk, but their mobility become limited with growth.

Find out how researchers have developed new mice models for SMA types 2 and 3.


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Type 4 is very rare. It usually appears during adulthood and leads to mild motor impairment. While symptoms can begin as early as age 18, they usually begin after age 35.

Read more on how a PCR mode can help determine SMA type.


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