ABSTRACT
Spinal Muscular Atrophy [SMA] consists of three types of disease including Werdnig Hoffman [SMA type1] which is an autosomal recessive degenerative motor neuron disease. These patients have abnormally in motor function of the muscles and will die in the first few years of life. The genetic locuses of all three types of SMA are on the chromosome numbers and a deletion in locus 5q11 -q13 will result in a variety of this disease. Case Report: heterozygous twin infants [boy and girl] were born from relative parents admitted to the hospital, one in three days after another, with upper respiratory tract infection, respiratory distress and coughing. They were hypotonic and had tongue fasciculation. They were intubated and ventilated in the PICU. SMA was suspected because of the general muscular weakness; therefore, biopsy and neurophysiologic studies were performed. Quadriceps muscle biopsy showed fascicular atrophy of muscle fibers and in genetic analysis of SMN1 gene in twin homozygous deletion of SMN1 gene at exon 7 was found. They became ventilator dependent and suffered respiratory failure and two weeks after their admissions in hospital, and with three day interval, died. It seems prudent to perform genetic assessments before having children in the parents who are close relatives especially after one affected child