Haploinsufficiency of 16.4 Mb from chromosome 22pter-q11.21 in a girl with unilateral conductive hearing loss.

We present the postnatal diagnosis of a de novo der(18)t(18;22)(p11.32;q11.21)pat, resulting in an unbalanced 45,XX,der (18)t(18;22) karyotype in a girl with conductive hearing loss on the left and ptosis of the right upper eye-lid. Unilateral ptosis was also observed in the patient’s 2 years and 8 months younger sister, who grows noticeably faster and appears to be a much quicker learner. After speech therapy the patient was eventually placed in normal school. The haploinsufficient 16.4-Mb region on chromosome 22pter→q11.21 contains 10 genes as well as many predicted genes, pseudogenes, and retrotransposed sequences with unknown functions. This observation may prove useful for prenatal dia…