BackgroundThe chromosomal region 11p15.5 harbours two imprinting centres (H19/IGF2:IG-DMR/IC1, KCNQ1OT1:TSS-DMR/IC2). Molecular alterations of the IC2 are associated with Beckwith-Wiedemann syndrome (BWS), whereas only single patients with growth retardation and Silver-Russell syndrome (SRS) features have been reported. CNVs in 11p15.5 account for less than 1% of patients with BWS and SRS, and they mainly consist of duplications of both ICs either affecting the maternal (SRS) or the paternal (BWS) allele. However, this correlation does not apply to smaller CNVs, which are associated with diverse clinical outcomes.Methods and resultsWe identified a family with a 132 bp deletion within the KCNQ1OT1 gene, associated with growth retardation in case of paternal transmission but a normal phenotype when maternally inherited. Comparison of molecular and clinical data with cases from the literature helped to delineate its functional relevance.ConclusionMicrodeletions within the paternal IC2 affecting the KCNQ1OT1 gene have been described in only five families, and they all include the differentially methylated region KCNQ1OT1:TSS-DMR/IC2 and parts of the KCNQ1 gene. However, these deletions have different impacts on the expression of both genes and the cell-cycle inhibitor CDKN1C. They thereby cause different phenotypes. The 132 bp deletion is the smallest deletion in the IC2 reported so far. It does not affect the IC2 methylation in general and the coding sequence of the KCNQ1 gene. Thus, the deletion is only associated with a growth retardation phenotype when paternally transmitted but not with other clinical features in case of maternal inheritance as observed for larger deletions.

We report the successful treatment using low-dose vigabatrin (21.5-34 mg/kg/day) of a 10-year-old girl with succinic semialdehyde dehydrogenase (SSADH) deficiency We verified that 4-hydroxybutyric acid (GHB) concentrations in serum, cerebrospinal fluid, and urine continuously decreased in parallel with significant clinical improvement. Our results suggest that GHB quantification in physiological fluids may be a useful laboratory parameter for monitoring efficacy of vigabatrin treatment in SSADH deficiency.

As allergy to wasp venom is a severe and potentially life threatening disease, false-negative test results need to be minimized. Therefore, the superiority of the Western blot with regard to sensitivity, specificity and overall efficiency makes this technique a valuable tool for its diagnosis.