a–c. Patient 1 at 4 weeks of age. Lateralized overgrowth (LO) of the (a) left cheek, (b) leg, and (c) foot with toes lengthening from great toe to fourth toe with space between fourth and fifth toe on larger left foot with bilateral feet with deep creases on plantar surface. Right foot measured 7 cm × 2.7 cm. Left foot measured 7.2 cm × 3.1 cm. d. Patient 1 at 9 months of age with esotropia, heterochromia, and LO of the left cheek. e Patient 3, critically ill with distended abdomen, diastasis recti, and right fifth toe hamartoma. f Patient 3, alive and well. g Patient 3, toe from multiple views. h Genome-wide view of single-nucleotide polymorphism (SNP) array B-allele frequency for patient 1 from blood. Genome-wide paternal uniparental isodisomy (GWpUPD) quantified to be 65%. i SNP array data viewed for part of chromosome 11 in order of highest percentage of GWpUPD to lowest: affected pancreas (80–85% GWpUPD), adrenal gland (65–60%), left leg skin (20%), and left side abdominal skin (5–10%). 11p15 is highlighted by the red box. j Percentage of GWpUPD by cell type in patients. ND not done.