NF1 microdeletion syndrome is a common dominant genomic disorder responsible for around 5% of type I neurofibromatosis cases. The majority of cases are caused by mutations arising within the NF1 gene. NF1 microdeletion carriers present a more severe phenotype than patients with intragenic mutations, including mental retardation, cardiac anomalies and dysmorphic features. Here, we report on two brothers with mental retardation presenting a microduplication of the NF1 microdeletion syndrome region detected by array-CGH analysis. Main phenotypic features are mental deficiency, early onset of baldness (15 years old), dental enamel hypoplasia and minor facial dysmorphism. The breakpoint regions coincide with the repeats, and the recombination hot spots shown to mediate NF1 microdeletion through NAHR. A screening of the patients' familial relatives showed that this microduplication segregates in the family for at least two generations. This result demonstrates that both deletion and duplication of the NF1 region, at cytogenetic band 17q11.2, give rise to viable gametes, even if only NF1 microdeletions have been reported until now. Our study reports seven cases of NF1 microduplication within one family. Similar phenotypic abnormalities were present in most of the individuals, however, two displayed a normal phenotype, suggesting a potential incomplete penetrance of the phenotype associated with NF1 microduplication.

suspicion was clouded by her pre-existing neurological state and concurrent sepsis causing diagnostic delay and significant morbidity. We believe that these predisposing events are common to all patients receiving high-dose chemotherapy for CNS lymphomas and that this complication is under-recognized. Evidence shows that cancer and its treatment is the leading case of WE in the paediatric population and that the diagnosis is commonly missed (Vasconcelos et al, 1999). We propose that prophylactic, parenteral thiamine should be administered to all patients receiving second-line anti-emetic therapy during high-dose chemotherapy for CNS malignancy.

Pathology of the bone marrow and spleen in a case of myelodysplastic⁄myeloproliferative neoplasm associated with t(8;9)(p22;p24) involving PCM1 and JAK2 genes

Cytogenetic analysis is of limited value in myeloma. Array CGH and FISH are highly specific tests allowing the identification of aberrations in virtually all cases. The two techniques are complementary and need to be combined in order to provide a comprehensive analysis of all clinically relevant aberrations in myeloma.

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