Objective: To establish a suitable human model for the study of the genetics of complex diseases. Methods: We have selected an Omani Arab population to provide the statistical power required to study the genetics of complex diseases with confidence. This model consists of five multigenerational highly inbred pedigrees, descending from a small number of founders just a few generations ago with environmental homogeneity, restricted geographical distribution, detailed records and well-ascertained and -validated pedigrees. Stringent criteria were adopted for defining the phenotypes of hypertension, diabetes mellitus, dyslipidemias and obesity. The SOLAR genetic software package was used to draw the pedigree structure. Results: Outstanding statistical power to detect susceptibility loci was obtained. Conclusions: This model represents a large homogeneous human family-based population for the study of genetic and environmental factors contributing to complex diseases.

This report describes a case of acute lymphoblastic leukaemia in which isochromosome 9q (i(9q)) was the sole acquired cytogenetic abnormality. The Immunophenotype showed positivity for CD3, CD4, CD5, CD7, CD8, CD10, CD71, CD117 and TdT, consistent with T cell acute lymphoblastic leukaemia (ALL). The chromosomal analysis of bone marrow showed 46,XY,i(9)(q10) in all the metaphases analysed. The bone marrow morphology was ALL-L2 as per the French-American-British criteria. Isochromosomes are rare chromosomal abnormalities in childhood ALL and the effect of i(9q) is not well established. The patient's good response to therapy with normal cytogenetics within a month of induction, and disease-free survival after bone marrow transplant are indicative of a good prognosis in such cases.

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