121 DISCORDANT MONOZYGOTIC TWINS WITH WILDERVANCK SYNDROME: A PROPOSED MODE OF INHERITANCE.

Wildervanck syndrome or cervico-oculo-acoustic syndrome is a recognizable malformation syndrome with major clinical features including Klippel-Feil sequence, Duane retraction syndrome, hypoplastic thumbs, and sensorineural hearing loss. Affected individuals with these findings must be differentiated from other malformation syndromes, including Townes-Brocks syndrome, Okihiro syndrome, Goldenhar syndrome, and MURCS association. Most previous reported cases with Wildervanck syndrome have been sporadic and female, although a few males with the condition have been described. Several modes of inheritance have been proposed, but X-linked inheritance appears most likely. We report an 18-year-old female with Wildervanck syndrome and her unaffected monozygous twin sister. She was the product of a twin pregnancy. She and her twin sister were born to her 23-year-old G1 mother and 25-year-old father after an uncomplicated pregnancy. The neonatal course was uneventful. She was previously diagnosed with Goldenhar syndrome based on the clinical features of a right epibulbar dermoid, small and dysplastic ears with bilateral preauricular tags, mild facial hypoplasia of the right, butterfly vertebrae. She has profound sensorineural hearing loss on the right and mild-moderate mixed hearing loss on the left. She has poor vision on the right, but left eyesight is normal. Development of gross motor skills was normal, although she had difficulty with balance. Her speech was delayed. Skeletal anomalies include hypoplastic thumbs with ankylosis, progressive scoliosis, congenital fusion in the lower cervical spine C5 and C6, and butterfly vertebrae in the upper thoracic spine. She also has Duane retraction syndrome. She had been clinically diagnosed with Okihiro syndrome, but complete SALL4 gene sequencing was not able to identify a mutation, and molecular analysis confirmed monozygousity. We propose that this female has Wildervanck syndrome with unaffected identical twin sister. Skewed X inactivation might explain discordance in the monozygotic twins, suggesting X-linked dominant inheritance. Review of the literature on Okihiro syndrome and Wildervanck syndrome will be included.