Haploinsufficiency of ANKRD11 (16q24.3) Is Not Obligatorily Associated with Cognitive Impairment but Shows a Clinical Overlap with Silver-Russell Syndrome.

Microdeletions in 16q24.3 are associated with intellectual disability and a specific phenotype, e.g. short stature and a prominent forehead. The 16q24.3 microdeletion syndrome shows a broad phenotypic overlap with the KBG syndrome, which is caused by mutations within the ANKRD11 gene. Furthermore, both KBG and the 16q24.3 microdeletion syndromes show clinical findings reminiscent of Silver-Russell syndrome (SRS), an imprinting disorder characterized by severe primordial growth retardation. In a cohort of patients referred as SRS, we previously identified a 16q24.3 deletion, but at that time, only patients with larger imbalances in 16q24.3 and intellectual disability had been published. Considering the recent description of the ANKRD11 gene as the causative factor for the 2 16q24.3-associated disorders, we now classified our patient as a 16q24.3 microdeletion syndrome patient exhibiting some characteristic features but normal intelligence. Our case illustrates the broad clinical spectrum associated with microdeletions, and we confirm that the 16q24.3 microdeletion syndrome is a further microdeletion syndrome with very variable expressivity. Indeed, our case is the first 16q24.3 patient of normal intelligence, but we assume that this variant is present in further mentally healthy probands which have not yet been tested. In conclusion, the detection of the 16q24.3 deletion in a proband of unremarkable intellectual capacities once again illustrates the need to perform molecular karyotyping in dysmorphic patients with normal intelligence.