Monosomy 7 predisposes to diabetes insipidus in leukaemia and myelodysplastic syndrome.

We studied the chromosomes in the bone marrow of 4 patients who had both diabetes insipidus (DI) and acute non-lymphocytic leukaemia. Clinical findings suggested that, in each case, myelodysplastic syndrome had preceded the onset of acute leukaemia. Two other such patients described in the literature had had a banded karyotype study of bone marrow cells. All 6 patients had deletions of chromosome 7. 3 had monosomy 7 as the sole cytogenetic abnormality, 2 had monosomy 7 associated with other clonal abnormalities and 1 had del(7)(q22) in association with other abnormalities. These data suggest that monosomy 7 or perhaps monosomy for 7q22-qter predisposes to DI. The mechanism by which the proposed predisposition is produced remains to be clarified.