Preventive examination of a 9-year-old girl revealed broad bridge of nose, narrow nasal passages, half-opened mouth, problems with lip joining, elongated lower third of face. The child presents with transitional occlusion. There is vertical gap 4-5 mm large from the 53 to the 64 tooth in the frontal region. Relationship of the first permanent molars complies with Angle's class I. The child pronounces hissing sounds indistinctly. Specify the most likely factor of occlusion deformation: