[The use of non-typical materials as a source of DNA in post-mortem diagnosis of spinal muscular atrophy].

Background And Purpose: Patients affected with SMA I usually die in early childhood before the end of the second year of life. Clinical diagnosis is often doubtful--without any molecular verification--and isolated DNA is not available. In such cases predicting the outcome of consecutive pregnancies is not possible. It appears, however, that the families often keep some relics of the diseased child, such as milk teeth, and pieces of umbilical cord; a dried drop of blood used for the Guthrie test in newborn screening may be available. The aim of this study was the post mortem molecular diagnosis of SMA based on samples of DNA isolated from such remnants.

Material And Methods: PCR technique was applied to amplify exons 7 and 8 of SMN gene; DraI and DdeI restriction enzymes were used to distinguish SMN1/SMN2 genes.

Results: The deletion of the SMN gene was found using DNA isolated from (1) a blot of dried blood, (2) a milk tooth and (3) dried umbilical cord of children who died several years ago without the molecular verification of the suspected SMA. In one case the analysis of DNA obtained from umbilical cord did not confirm the diagnosis of SMA.

Conclusions: Our results showed that biological materials such as those mentioned above may be kept for a long period of time without degradation of DNA, which is still satisfactory for molecular diagnosis of SMA. This is very important for genetic counseling and offering a prenatal test to the families concerned.