Broad phenotypic spectrum of germ line 7p12.1 microdeletions encompassing the IKZF1 gene includes predisposition to acute lymphoblastic leukemia.

Microdeletions of 7p12.1 encompassing the IKZF1 gene locus are rare, with few cases reported. The common phenotype includes intellectual disability, overgrowth, and facial dysmorphism accompanied, albeit rarely, by congenital anomalies. Haploinsufficiency of IKZF1 predisposes individuals to childhood acute lymphoblastic leukemia (ALL). In this study, we comprehensively analyzed the frequency of 7p12.1 deletions among 4581 Polish individuals who underwent chromosomal microarray testing for unexplained developmental delay, intellectual disability, and/or congenital anomalies. Two unrelated individuals (0.04%) with a de novo interstitial 7p12.1 microdeletion encompassing IKZF1 were identified. One developed ALL. Analysis of the incidence and the phenotype of constitutional 7p12.1 microdeletion, which based on the previously annotated patients data in public databases and literature reports, revealed 21 cases including five patients diagnosed with ALL.