Phenotype is apparent at birth. Craniofacial
abnormalities include macrocephaly, flat midface, flat nose root,
and cleft palate. Occasional association with Pierre-Robin syndrome has been reported. Tracheal
cartilage is abnormal, and tracheomalacia may occur as a result. The chest may be short and narrow, but ventilation and perfusion of the lungs usually remain unaffected. The
vertebral column often has platyspondylia with anterior wedging of the vertebral bodies,
coronal clefting of the thoracolumbar vertebral bodies, and occipitoatlantal instability.
Kyphoscoliosis and/or lumbar hyperlordosis may develop. In an extensively studied patient, there was bony fusion between the anterior arch of the
atlas and the odontoid and between the posterior arch of the atlas and the cranial base.
Growth usually is retarded. The limbs are characteristically very short secondary to short
tubular bones. The epiphyses are large and deformed and the metaphyses broad resulting in
so-called “dumbbell” shape, as a consequence of delayed epiphyseal ossification
resulting in mega-epiphyses. The joint space is narrow with limited joint mobility.
Early-onset myopia, retinal detachment, and sensorineural hearing loss are common findings. Patients often present for repair of umbilical
and inguinal hernias.