Prenatal diagnosis of spinal muscular atrophy in Turkish families.

Prenatal diagnosis of childhood proximal spinal muscular atrophy (SMA) is carried out by the detection of homozygous deletions of survival motor neuron (SMN; exons 7 and 8) and neuronal apoptosis inhibitory protein (NAIP; exons 5 and 6) genes located in 5q13 chromosomal region. In Hacettepe University, Department of Medical Biology, 203 postnatal molecular diagnoses of SMA have been carried out since October 1994 and prenatal diagnosis in subsequent pregnancies to couples who previously had an affected child became possible. Between January 1996 and December 1999 totally 41 SMA families were analyzed by detecting homozygous deletions of SMN and NAIP genes for prenatal counseling. Fetal DNAs were obtained from amniotic fluid and chorionic villus samples. 8/41 (20%) fetal samples were found to be affected and these pregnancies were terminated. It was interesting to find that 2 fetuses had only SMN deletions, however their affected siblings had both SMN and NAIP gene deletions.