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A child is evaluated for iris colobomas and preauricular tags. CMA reveals a small supernumerary marker chromosome derived from chromosome 22.
- Supernumerary marker chromosome: inv dup(22)(q11.2)
- Tetrasomy of 22pter→22q11.2
- Variable phenotype (due to mosaicism)
- Ocular coloboma (iris, retina)
- Preauricular tags/pits
- Anal atresia (some patients)
- Cardiac defects (TAPVR)
- Renal malformations
- Normal to mild intellectual disability
- Chromosomal microarray (CMA) detects the gain at 22pter→q11.2 and is the first-line test when a marker is suspected
- Karyotype with FISH (chromosome 22 probes) confirms the small supernumerary marker chromosome as inv dup(22) and characterizes its structure
- Mosaicism is common, so report the proportion of cells carrying the marker; a low-level marker on blood may be missed
- Echocardiogram for cardiac defects (TAPVR) and renal ultrasound for urinary tract malformations
- Ophthalmology evaluation for coloboma and vision monitoring
- Assessment for anal atresia and other anorectal anomalies in the newborn period
- Developmental monitoring with early intervention as needed
Remember "CCAATT": Cardiac anomalies, Coloboma, Anal Atresia, Tags (preauricular), Twenty-two (tetrasomy 22).