Patients with Lambert syndrome present with
facial dysmorphism related principally to abnormal development of the first
branchial arch (malar hypoplasia, macrostomia, preauricular tags, and/or
auricular atresia). Other malformation may include clubfeet, inguinal
hernia, and hypospadias. Congenital heart defects (e.g., ventricular septal
defect) have been reported. Patients develop cholestatic jaundice related to
a paucity of intrahepatic biliary ducts and moderate-to-severe mental
retardation.