Editor—Partial or total glucocerebrosidase (GBA) gene deletions and genetic rearrangements between the functionalGBA gene and its highly homologous pseudogene (ψGBA) have been reported as pitfalls in diagnostic mutation analysis leading to incorrect genotyping in Gaucher disease (GD, MIM 230800, 230900, 231000). In particular, homozygosity for 1226G/1226G has been misdiagnosed in the presence of both deletions and complex alleles.1-6Because of the necessity selectively to amplify functionalGBA sequences from unprocessed pseudogene (ψGBA) ones, currently available PCR based techniques make use of primers either in or around the 55 bp pseudogene gap.7-12 Therefore, if a deletion or a recombination event is present in sites where one of the primers has to bind, the use of these oligonucleotides that hybridise only with the other allele may produce an apparently homozygous genotype, which can lead to incorrect genotyping and unreliable genetic counselling for patients and their families. Thus, as soon as the rapid screening techniques proved occasionally to be misleading in diagnostic mutation analysis, the laboratories that make use of PCR based methods were warned to pay particular attention to this fact.

To ascertain accidental misgenotyping in a panel of GD patients, molecularly characterised by conventional techniques,13 we have adapted a simple non-isotopic PCR based method from the isotopic one described by Beutler and Gelbart.1 The procedure is based on simultaneous GBA andψGBA amplification and subsequent comparison of light intensity between the PCR fragments of the gene and the internal control pseudogene. The approach has been used to re-examine 34 patients who were previously genotyped as homozygotes (15 for 1448C (L444P), 14 for 1226G (N370S), one for 1342C (D409H), and four for unique mutations) as well as all patients who had one or both alleles still unidentified, 42 and three respectively. …