|
|
|||
Myotonic dystrophy is a common autosomal dominant disorder with an estimated incidence of 1 in 8000; however, since mildly affected individuals may not be diagnosed, it is likely to have a higher incidence. The clinical presentation of this disease shows striking variability even within the same family and it has been noted for some time that this disease shows anticipation (the clinical features become more severe and generally have an earlier age of onset of each subsequent generation). With the identification of the myotonin protein kinase gene which is responsible for myotonic dystrophy came a better understanding of these phenomena. The mutation causing myotonic dystrophy was found to be an unstable polymorphic trinucleotide CTG repeat. In affected individuals, this region shows expansion from approximately 50 to several thousand repeats in cases of congenital myotonic dystrophy. The size of the allele correlates with the age of onset and severity of the disease; however, these data are not precise enough to be used for predictive purposes at the present time. Reasons for Referral:
Testing Methodology:Direct Mutation Analysis: PCR analysis across the CTG repeat region to determine allele size(s). This assay is particularly sensitive for identifying alleles between 30-80 repeats. Southern analysis: The MDY1 probe from the myotonin protein kinase gene is used to identify large expansions of the CTG repeat region with Nco I or BamHI digested DNA. Specimen Requirements:Blood: EDTA (purple-top) tubes: Adults: 14
cc; Child: 6
cc; Infant: 2-3 cc Turnaround Time:3 weeks CPT Codes and Prices:Index: 83898, 83891, 83892x2, 83894x3, 83896x2, 83897x2, 83912 Shipping InformationForms: >> DNA
Requisition Test Codes:
Index: 6041 |