Medicines for Spinal muscular atrophy

What it is

Spinal muscular atrophy (SMA) is a rare genetic condition that causes progressive muscle weakness and wasting. It occurs because of a problem affecting the motor neurons — the nerve cells in the spinal cord that control muscle movement — which are lost or do not work properly, so the muscles they control become weak and waste away. SMA is caused by a change (mutation) in a particular gene (usually the SMN1 gene), and is inherited in a way that means a child is affected when they inherit the faulty gene from both parents (who are usually unaffected carriers). SMA mainly affects the muscles used for movement, and often those closer to the centre of the body, leading to weakness that can affect activities such as sitting, standing, walking, and, in more severe forms, breathing and swallowing. There are different types of SMA, which vary greatly in severity and the age at which they begin: the most severe forms begin in infancy and cause significant weakness affecting movement, breathing, and swallowing; while milder forms begin later (in childhood or adulthood) and cause slower-progressing weakness with a wider range of effects. This variability means the outlook and needs differ greatly between types. A very important and hopeful development is that the treatment and outlook for SMA have been transformed in recent years by new treatments that target the underlying genetic problem — including medicines and gene therapy that can slow or alter the course of the disease, and which are most effective when started early, before too much damage has occurred. This is why early diagnosis is so important, and newborn screening for SMA is being introduced in some places to allow early treatment. Alongside these treatments, SMA is managed with supportive and multidisciplinary care (such as physiotherapy, respiratory and nutritional support, and equipment) tailored to the person’s needs. The key messages are that SMA is a rare genetic condition causing progressive muscle weakness, that it varies greatly in severity, and that newer treatments targeting the genetic cause have transformed the outlook — especially with early diagnosis and treatment — alongside supportive care.

How it is treated

Spinal muscular atrophy is managed by specialist multidisciplinary teams, and its treatment has been transformed by newer therapies that target the underlying genetic cause, alongside supportive care; early diagnosis and treatment are very important. Diagnosis is made through genetic testing (which confirms the SMA gene change), along with clinical assessment and other tests, and is increasingly being made early — newborn screening for SMA is being introduced in some places, which is significant because early treatment, before too much motor neuron damage has occurred, gives the best results. The major advance in SMA is disease-modifying treatment that targets the underlying genetic problem: there are now treatments — including medicines that increase the production of the needed protein, and gene therapy that provides a working copy of the gene — that can slow, halt, or alter the progression of SMA, and these have significantly changed the outlook, particularly for the more severe forms when treatment is started early. These treatments are provided through specialist centres, and the choice and suitability depend on the type of SMA, the person’s age and situation, and current guidance; this is a rapidly developing area. Alongside disease-modifying treatment, comprehensive supportive and multidisciplinary care remains very important, tailored to the person’s type of SMA and needs, and may include: physiotherapy and occupational therapy to support movement, function, and independence, and to manage the effects of weakness; respiratory (breathing) support and monitoring, which is important particularly in more severe forms; nutritional support and help with feeding or swallowing where affected; orthopaedic care (for example for the spine and joints); equipment and mobility aids; and support for the person and family across health, development, education, and daily life. The aims are to maximise function, independence, and quality of life, and to manage the effects of the condition. Because SMA is genetic, genetic counselling is offered to families to discuss the condition, inheritance (including carrier status), and family planning. The outlook varies with the type of SMA and, importantly, with access to and timing of the newer treatments, which have improved outcomes considerably. The reassuring and hopeful messages are that, although SMA is a serious, rare genetic condition, newer treatments targeting the genetic cause have transformed the outlook — especially with early diagnosis and treatment — and that comprehensive multidisciplinary care supports function, independence, and quality of life; so early diagnosis (including through newborn screening where available) and specialist care are key.