Spinal Muscular Atrophy: An Undeserved Inheritance

Spinal Muscular Atrophy, or SMA, is one of a group of hereditary diseases is one of those silent social issues that nobody talks about very much in any society. Heartbreaking for those affected, one cannot fail to be affected when confronted with the realities of the condition, even in a brief encounter. The global ‘face’ of SMA of course is prominent physicist, and author, Sir Stephen Hawking, while Hollywood star Keira Knightley is the Patroness of the SMA Trust. Others, like Ellie Darby Prangnell are prominent media influencers, Chanel Washington has been accepted to Harvard, Princeton, Columbia, Georgetown, Brown, Duke, Pomona and Washington universities. And Shane Burcaw and fiancée Hannah, are YouTube sensations who boast a ‘complete’ relationship, so SMA does have some positive outcomes, but what is it? SMA progressively destroys the nerve cells of the spinal cord and brain stem that control skeletal muscular activities such as walking, speaking, swallowing and breathing. The cells, motor neurons, usually facilitate the body’s limb and facial movement and due to their lack of function among sufferers, significant wasting occurs and twitches develop. The condition occurs when both parents have a defective survival motor neuron 1 gene, which is responsible for producing the protein for maintaining the healthy functionality of the motor neuron system. The defect can be diagnosed, though carriers may be asymptomatic, however blood tests can identify 95 per cent of most types of SMA and electromyography, nerve conduction tests, and muscle biopsies can also reveal carriers of the defective gene. Statistics say that if you have a brother or sister with SMA, you have a 2 in 3 chance of being a carrier. If you have a niece or nephew with SMA, a 1 in 2 chance, an aunt or uncle, a 1 in 3 chance, or a 1 in 4 chance if you have a cousin with it. The blood test is a small price for knowing. Cures, or treatments, are rare and expensive, with the USFDA approving three treatments thus far. Nusinersin (Spinraza $125,000 per injection) is for children and adults and has been in use since 2016. It is injected several times directly to the spinal cord, in quick succession, then every four months subsequently, to stimulate another gene to produce more protein, and is around 40pc successful. 2019 saw Onasemnogene abeparvovec-xioi (Zolgensma $2.25 million) approved as a one-time treatment for children under 2 years and replaces the SMN1 gene with a synthetic alternative via a catheter and has demonstrated positive outcomes to date. The third, Risdiplam (Everysdi, $340,000 pa), was only approved in August 2020, and prevents the disruption to protein production with oral doses every day. Initial responses show a 41pc improvement in muscle function after a year of the treatment from those 2 months of age and older. These prohibitive costs place curative treatments out of most people’s reach. The prognoses vary considerably, dependent upon the treatment undertaken, and the reality is that without treatment few experience positive outcomes, and though patients may appear to be stable for extended periods of time, improvement cannot be expected without treatment. This is an insidious disease, undeserved by any, but if we are vigilant, and do not ignore the hereditary markers, we can avoid its consequences. In fact, Spinal Muscular Atrophy, UK, advised in its 2018 awareness campaign, that one person in every rail carriage full of people carries the genetic mutation that causes SMA, around 1 in 40. How sobering is that statistic?