Abstract

Imprinting disorders (IDs) are a group of rare congenital diseases affecting mainly growth, development and metabolism. The cause of IDs is an aberrant expression of imprinted genees due to genetic or epigenetic abnormalities. Although each of the IDs has its own specific clinical features, the symptoms are often overlapping, atypical or mildly expressed. Because of the high variability of the clinical phenotype and molecular alterations, many cases remain undetected and the exact prevalence of IDs is not known. At present, there are ten clinically recognized IDs: Prader-Willi syndrome (PWS), Angelman syndrome (AS), Beckwith-Wiedemann syndrome (BWS), Silver-Russell syndrome (SRS), Temple syndrome (TS), Kagami-Ogata syndrome (KOS), transient neonatal diabetes mellitus (TNDM), pseudohypoparathyroidism (PHP), maternal uniparental disomy of chromosome 20 syndrome (UPD(20)mat) and precocious puberty syndrome (CPP). Moreover, many cases of simultaneous aberrant methylation at multiple imprinted loci or multilocus methylation defects (MLMD) have been reported in the literature of recent years. Here we describe the clinical features, molecular etiology and diagnostic methods of IDs, as well as present cases of BWS and SRS in two Estonian children.