Isochromosome 18p

Epidemiology and Etiology:

• De novo usually

Common sites:

Gross features:

• Low birth weight
• Microcephaly
• Facies:
• Round or oval shape
• Low-set ears
• High eyebrows
• Short palpebral fissures
• Small nose
• Long philtrum
• Small mouth
• Hypotonia at birth
• Spasticity by 2^nd year
• Camptodactyly or adducted thumbs

Histologic features:

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

Other features:

• Mental retardation
• At least moderate
• Seizure disorders common
• Feeding difficulties

References:

· Callen DF, Freemantle CJ, Ringenbergs ML, et al. The isochromosome 18p syndrome: confirmation of cytogenetic diagnosis in nine cases by in situ hybridization. Am J Hum Genet. 1990;47(3):493-8.