Clavicular pseudoarthrosis, anomalous coronary artery and extra crease of the fifth finger-previously unreported features in individuals with class II 1q21.1 microdeletions

Submicroscopic deletions of two adjacent regions within chromosomal band 1q21.1 were recently associated with two distinct phenotypes: A deleted region of 200–500 kb was found in individuals with Thrombocytopenia Absent Radius syndrome (TAR). Deletion in another region of about 1.25 Mb that is located just telomeric of the TAR region, referred to as distal 1q21.1 region, was found to be associated with a phenotype of cognitive impairment, congenital heart defects and other variable manifestations. A significant proportion of individuals with either of the two deletions did not have phenotypic abnormalities. More than 40 individuals with distal 1q21.1 deletions have been reported to-date. A proportion of them (9 reported individuals) had larger (>2 Mb) deletions involving both the TAR and the distal 1q21.1 regions, referred to as class II deletions. We describe here four additional individuals from two families with such class II deletions, who presented with previously unreported manifestations: clavicular pseudoarthrosis and anomalous origin of the coronary artery in the proband of the first family; an extra transverse crease of the fifth finger, segregating in two of the three deletion carriers in the second family. Previously reported features, associated with such microdeletions – absolute or relative microcephaly, cognitive impairment and short stature, were variably observed in the reported individuals. This report expands the phenotypic spectrum associated with class II 1q21.1 deletions, and demonstrates striking phenotypic variability even within the same family.