What is SMA

Spinal muscular atrophy (SMA) is a rare neuromuscular disorder characterized by loss of motor neurons and progressive muscle wasting, often leading to early death.

The disorder is caused by a genetic defect in the SMN1 gene, which encodes SMN, a protein widely expressed in all eukaryotic cells (that is, cells with nuclei, including human cells) and necessary for survival of motor neurons. Lower levels of the protein results in loss of function of neuronal cells in the anterior horn of the spinal cord and subsequent system-wide atrophy of skeletal muscles.

Spinal muscular atrophy manifests in various degrees of severity, which all have in common progressive muscle wasting and mobility impairment. Proximal muscles, arm and leg muscles that are closer to the torso and respiratory muscles are affected first. Other body systems may be affected as well, particularly in early-onset forms of the disorder. SMA is the most common genetic cause of infant death.

SMA Type I is the most severe and the most common- is usually diagnosed during an infant’s first six months. Babies with SMA type I face many physical challenges, including muscle weakness and trouble breathing, coughing, and swallowing. They may need breathing assistance or a feeding tube. Type I is often fatal early on in life. 60% of all SMA cases are type I. SMA type I is also know as Werdnig-Hoffmann disease.

SMA Type II is usually diagnosed after six month of age, but before two years of age. The first sign is often a delay in meeting motor milestones, or failing to meet milestones entirely. Individuals affected by SMA type II can typically sit up without help, though they may need assistance getting into a seated position, but they are unable to walk and will require a wheelchair.

SMA Type III is usually diagnosed after 18 months of age, but before three years of age. However, SMA type III can be diagnosed as late as the teenage years. Individuals affected by SMA type III are initially able to walk, but have increasingly limited mobility as they grow and eventually, many need to use a wheelchair. Type III is also called Kugelberg-Welander disease or juvenile SMA.

SMA Type IV is very rare. It usually surfaces in adulthood, and it leads to mild motor impairment.  While symptoms can begin as early as age 18, they usually begin after age 35.


Diagnosis is based on a history of clinical examinations, and is then confirmed by genetic testing. Electromyography and muscle biopsy are also performed.


The treatment of the disease has been symptomatic only until recently. A new drug, Nusinersen, is now available. It increases the level of full-length SMN protein. Other potential new drugs are undergoing clinical trials. Clinical studies dedicated to the future treatment of this condition are underway in the Czech Republic and abroad. The results of studies can be view on Cure SMA.

Individuals diagnosed with this disease will spend their whole life in the care of a multidisciplinary team of professional such as neurologists, orthopedics, pneumologists, physiotherapists, nutritionists etc.

Patients, depending on the degree of the illness, need various compensatory aids (electric wheelchair, special seats, orthoses..) and they’re fully dependent on the care of other people.


In addition to the medicine, intensive rehabilitation or spa care is also important for the patients. The primary focus is overall body care and prevention of soreness and spinal deflection (scoliosis). Care must be taken to avoid breathing problems which are an integral part of SMA. It is necessary to work with various aids and to combine physiotherapeutic methods, fitness exercises and neurophysiological exercises. These include reflex locomotion, sensomotor stimulation, aquatherapy, hippotherapy and other highly specialized methods.

How is life with SMA?

This congenital genetic disease greatly affects the lives of children (patients). They will spend the most of it on wheelchairs, using various aids for breathing support. Children are bold, smart, more or less successfully integrated into ordinary schools, and fortunately usually endowed with a specific sense of black humor that helps them gracefully overcome collisions with barriers in human behavior.

In normal tasks, such as dressing, eating food, they’re completely dependent on the care of other people. They need assistance 24 hours a day.

You can read more about SMA at Cure SMA website Cure SMA

How to explain to children what spinal muscular atrophy is when they ask why Sofia is in a wheelchair?

Biogen and the SMA community have created a beautiful fairy tale about little Zac, where it is simply explained what SMA is. You can watch it here: Zac’s Play Day.

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