Trisomy 22 Mosaicism and Normal Developmental Outcome: Report of Two Patients and Review of the Literature

Mosaic trisomy 22 is known to be compatible with life. However, there are fewer than 20 reports in the literature of live born children and even fewer reports describing their neurodevelopmental outcome. We report on two girls with mosaic trisomy 22 and normal development at ages 7 and 5 years. Both girls had characteristic dysmorphic features including flat nasal bridge, preauricular pits, epicanthic folds, and 5th finger clinodactyly. They also had left-sided hemihyperplasia and short stature. In addition, one of them also had ventricular non-compaction and probable asplenia, two unique features not previously reported. In review of the literature, prenatal and postnatal growth failures were the most common complications of mosaic trisomy 22. Skeletal abnormalities including body asymmetry and 5th finger clinodactyly were also common. While the majority of patients with mosaic trisomy 22 had abnormal cognitive development, normal development has also been documented. It is conceivable that children with trisomy 22 mosaicism, with minimal physical findings and normal development are under diagnosed. Our patients further highlight this potential for normal cognitive outcome and draw attention to possible skewing of unfavorable prognosis for the final developmental outcome in this population. Appropriate information regarding developmental outcome is critical for genetic counseling, especially in prenatal situations.