This very rare form of SMA appears in infancy and causes severe muscle weakness and difficulty breathing. Children often have mis-shapen joints that make movement difficult. Babies who are severely affected may be born with broken bones.

There is only limited information about X-linked SMA because it is so rare, but your child’s medical team will be able to discuss how it will affect your child and how to manage symptoms for maximum comfort and quality of life.

The affected gene is:

• UBA1 (X sex chromosome)¹‾²

Further information can be found here.

X-linked SMA has an X-linked Recessive inheritance pattern.

Little is known about the biology of X-Linked SMA. However, in 2023 Muscular Dystrophy UK awarded a grant to Professor Thomas Gillingwater and colleagues to characterise a newly generated mouse model. This is much needed to test new treatments for the condition.

Read more on their website >

Though not a substitute for professional medical advice, the US National Library of Medicine, Genetics Home Reference provides more information. Click here to read more.

SMA UK

• Phone: 01789 267520
• Email: office@smauk.org.uk
• Website: www.smauk.org.uk

Provides information and support foranyone in the UK affected by any form of SMA.

Contact 

• Phone: 0808 808 3555
• Website: www.contact.org.uk

Provides information and support for families with children with a disability.

Children’s hospices
Located throughout the UK, these offer a wide range of services and support to eligible children and families; some also offer short breaks. Details of hospice services are available from Together for Short Lives and more information is available on their website.

1. Ramser et al. (2008) ‘Rare missense and synonymous variants in UBE1 are associated with X-linked infantile spinal muscular atrophy’, American Journal of Human Genetics, 82, pp. 188-193.

2. https://www.omim.org/entry/301830 (accessed 25th August 2022)