Spinal muscular atrophy: frequent cause of congenital hypotonia in Morocco

• Published in: Archives de pédiatrie : organe officiel de la Société française de pédiatrie Vol. 18; no. 12; pp. 1261 - 1264
• Main Authors: Sbiti, A, Ratbi, I, Kriouile, Y, Sefiani, A
• Format: Journal Article
• Language: French
• Published: France 01.12.2011
• Subjects: Child, Preschool; DNA; Electromyography; Exons; Gene Deletion; Genetic Counseling; Genetic Testing; Genome, Human; Humans; Infant; Infant, Newborn; Morocco - epidemiology; Muscle Hypotonia - congenital; Muscle Hypotonia - diagnosis; Muscle Hypotonia - epidemiology; Muscle Hypotonia - genetics; Prevalence; Spinal Muscular Atrophies of Childhood - diagnosis; Spinal Muscular Atrophies of Childhood - epidemiology; Spinal Muscular Atrophies of Childhood - genetics; Survival of Motor Neuron 1 Protein - genetics; Survival of Motor Neuron 2 Protein - genetics; Morocco
• ISSN: 1769-664X
• DOI: 10.1016/j.arcped.2011.09.025

Congenital hypotonia is a non specific symptom frequently seen in newborns and infants, and whose etiological diagnosis is often difficult due to the lack of specialized and affordable explorations. Childhood-onset proximal spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by degeneration of the anterior horn cells of the spinal cord, leading to progressive paralysis with muscular atrophy. In more than 95% of the cases, it results from deletion of exon 7 of the SMN gene localized on 5q13, easily identified by molecular biology. To determine the prevalence of the deletion of exon 7 of the SMN gene in congenital hypotonia with an unknown cause in Morocco. We investigated the deletion of exon 7 of the SMN gene in 87 newborns and infants with congenital hypotonia. The cause of congenital hypotonia could not be determined in 60 of them, while 27 had electrophysiological evidence for an involvement of the anterior horn cells. The homozygous deletion of the SMN gene was detected in 23 of the newborns with unknown cause for hypotonia (38%) and in 21 of the infants whose electromyogram suggested infantile spinal amyotrophy (78%). This study underlines the advantages of a systematic search for the deletion of exon 7 of the SMN gene in every infant suffering from congenital hypotonia due to an unknown cause, particularly when the child's vital prognosis is at stake. This genetic test, easily implemented, should be systematically proposed after an attentive clinical evaluation in countries where the etiological diagnosis of congenital hypotonia is not systematic.