Multiplex ligation-dependent probe amplification as first mutation screening for large deletions and duplications in haemophilia.

INTRODUCTION: Molecular characterization has shown a wide mutational spectrum underlying haemophilia A (HA) and haemophilia B (HB). Different molecular assays have allowed laboratories to perform genetic testing for F8 and F9 mutations.

AIM: Recently, multiplex ligation-dependent probe amplification (MLPA), a simple technique for relative quantitation of targeted genomic regions, has been introduced in HA and HB for detection of large deletions and duplications. We want to verify if MLPA might be used at the beginning of the molecular investigation.

METHODS: We used it to test 22 patients with suspected large deletions, nine patients negative for mutation detection by other methods and finally, 45 new patients as their first screening test.

RESULTS: Carrier status was also established in 28 related females and gross rearrangements were also searched for by MLPA in 19 females with reduced FVIII or FIX levels. All suspected deletions were confirmed apart from two patients. In patients with a negative screening test, MLPA revealed one large duplication, while in two patients where MLPA was used as the first screening step, an exon duplication was detected. In females with reduced FVIII or FIX, no large deletions or duplications were found.

CONCLUSIONS: Owing to its simplicity, MLPA seems useful at the beginning of the molecular investigation, saving all the following steps, where positive. Single exon deletion diagnosis requires caution due to the risk of misdiagnosis, but benefits of MLPA appear to overcome the pitfalls.