Intrauterine diagnosis of SMA type 1 and early initiation of therapy: case report

Case presentation: Female patient, second daughter of a healthy couple, was first bought for neuropediatrician evaluation with three days old already with the diagnosis of spinal muscular atrophy 5q (SMA) type 1. The firstborn of this couple had the same diagnosis (deceased one month after her first birthday) therefore they decided to test the second child while still in the uterus. PCR (Polymerase Chain Reaction) for SMA was performed in a villochorial sample, which showed a homozygous deletion of exon 7 SMN1. On physical examination, she presented mild global hypotonia, tongue myofasciculation, suction reflex and no apparent malformations. She scored 22 of 64 on CHOP-INTEND evaluation. MLPA (Multiplex Ligation-Dependent Probe Amplification) collected, showing two copies of SMN2. At the end of her first month of life, hypotonia was more accentuated. The patient underwent the first intrathecal infusion of nusinersen at thirrty five days of life. Three months old evaluation, (after three infusions) improvement of hypotonia was observed. The patient had partial cervical support, social smile, palmoplantar prehension and was following human face, scoring 39 of 64 on CHOP INTEND. Tongue myofasciculation was not observed but polymyoclonus of the hands was present. No ventilation support was required, and feeding was orally.

Discussion: Spinal muscular atrophy (SMA) presents progressive degeneration of motor neurons located in the anterior horn of the spinal cord and has an incidence of 1 in every 10,000 births. SMN1 gene mutations comprise the most common form of the disease and their severity is related to the age of onset of symptoms. It is classified into types I, II, III and IV. Type I presents symptoms before six months of life and has a more severe presentation, with death occurring in most cases before two years of life. Nusinersene is indicated in cases of mutation or deletion of SMN1, and acts by increasing the amount of functional survival motor neuron (SMN) protein from the SMN2 gene.

Final comments: With the initiation of nusinersen therapy, a significant improvement in hypotonia was observed, the patient continued with oral feeding (breast on demand), without sialorrhea, presented fully expanded chest, without tachypnea or dyspnea, which reinforces that nusinersen therapy has been modifying the course of the disease, offering better quality and life expectancy for patients with SMA.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
18 September 2023