"This is a major step forward": a decisive step against spinal muscular atrophy with neonatal screening

Since September 1, infantile spinal muscular atrophy (SMA), a rare and serious genetic disease – along with two other diseases (1) – have been among the pathologies systematically screened for at birth.

Carried out using a simple blood sample in the first days of life (Guthrie test), this widespread screening makes it possible to detect SMA even before the onset of symptoms.

This is a major step forward, given that until now, babies were often diagnosed too late, when damage to nerve cells had already taken hold.

" This is a crucial step forward," insists Dr. Caroline Perriard, a pediatric neurologist at Lenval Hospital and co-coordinator of the Reference Center for Childhood Neuromuscular Diseases with Dr. Christian Richelme. " The earlier we intervene, the more we can change the life trajectory of these children. "

A severe genetic disease

To understand the importance of this widespread screening, we must understand the nature of spinal muscular atrophy, a neuromuscular disease which progresses very rapidly from the first months of life.

" It is caused by an abnormality in the SMN1 gene, which is essential for the production of a protein essential for the survival of motor neurons—the nerve cells that transmit orders from the brain to the muscles. When this gene is defective, the motor neurons gradually degenerate, causing increasing muscle weakness ," explains the pediatric neurologist.

In infants, the first symptoms generally appear within the first 6 months of life, for the most severe and early form, spinal muscular atrophy type 1.

" These are often very hypotonic babies, who may have difficulty feeding or breathing. During the clinical examination, a distinctive sign is the absence of osteotendinous reflexes (the absence of reflex contraction of a muscle)," explains the specialist.

In its most severe form, the disease progresses rapidly and, if left untreated, can be fatal before the age of two.

Early detection that changes everything

In recent years, gene therapy has significantly improved the prognosis. " A single injection (Zolgensma) replaces the diseased gene with a healthy one, treating the disease at its source and thus preserving motor neurons."

At the Nice referral center, five children with SMA who were symptomatic benefited from this therapy before widespread screening was implemented. "They were diagnosed quite early. They are doing well and have few after-effects," emphasizes Dr. Perriard.

But to be fully effective, gene therapy must be administered in the first days of life, before the onset of symptoms, as demonstrated by the Depisma program (see box).

Since Monday, widespread neonatal screening for SMA has enabled this early detection and thus changed the lives of children. " It's a real opportunity for them to have normal motor development," says Dr. Perriard.

Fast and coordinated support

To ensure effective monitoring, a structured care pathway has been put in place. In the event of a positive screening, the referring pediatric neurologist (Dr. Cécile Halbert for the Marseille region, Dr. Perriard for the Nice region) is contacted and arranges a consultation with the parents and the baby as soon as possible.

The diagnosis is confirmed by genetic testing, followed by a comprehensive assessment to prepare for treatment. The decision to initiate gene therapy is always made collectively at the national level, and the treatment is currently being administered at the Timone University Hospital in Marseille. "Soon, this therapy will also be available in Nice, which will greatly facilitate the journey for the families concerned."

After the injection, the child remains hospitalized, usually for a week, under close observation. " There are risks of inflammation that can affect the liver, heart, or other organs. We monitor all of this very closely," the doctor explains.

Subsequently, the child receives blood tests and regular consultations for optimal monitoring. " Today, spinal muscular atrophy is no longer inevitable, and we have the means to offer these children a radically different future."

1. Since Monday, newborn screening has expanded to include, in addition to spinal muscular atrophy, two other rare and serious diseases. - Severe combined immunodeficiency (SCID), which prevents the baby from developing an effective immune system, making it very vulnerable to deadly infections. With early detection, a bone marrow transplant performed within the first two months can save these children. - Very long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency, a metabolic disease that blocks the conversion of certain fats into energy, is now also detected at birth. Prompt treatment, including appropriate nutrition, can prevent serious complications.