Prenatal diagnosis of spinal muscular atrophy in Egyptian families

ABSTRACT

Spinal muscular atrophy [SMA] is the second most common autosomal recessive neuromuscular disorder and a common cause of infant disability and mortality. It affects the anterior horn cells of the spinal cord and motor cranial nuclei leading to bilateral progressive paralysis of peripheral muscle and death due to affection of respiratory muscles. SMA patients are classified into three clinical types based on age of onset and severity of symptoms. About 94% of patients have homozygous absence of exon 7 in the survival of motor neuron 1 [SMN1] gene [homozygous delta 7SMN1 mutation]. The neuronal apoptosis inhibitory protein [NAIP] gene was found to be more frequently deleted in the severest form of the disease [type I]. This study aimed to comment on the implementation of genetic counseling and prenatal diagnosis of SMA for 37 fetuses from 27 Egyptian couples at risk of having an affected child. The homozygous delta 7SMN1 mutation and the deletion of exon 5 of the NAIP gene were detected using PCR-RFLP and multiplex PCR methods; respectively. Five fetuses showed homozygous delta 7SMN1 mutation and deletion of NAIP gene exon 5. In conclusion, prenatal diagnosis is an important tool for accurate diagnosis and genetic counseling that help decision making in high risk families