Insertions

Epidemiology and Etiology:

· Rare, similar to other 3-break rearrangements

· 1 in 5000 live births (intrachromosomal)

· 1 in 80,000 (interchromosomal)

· Direct vs inverted

· Intrachromosomal vs interchromosomal

· Interchromosomal:

· 85% are inherited

· Maternal usually

Common sites:

·

Gross features:

·

Histologic features:

·

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

·

Other features:

· 15% overall risk for an unbalanced liveborn child for intrachromosomal insertions (n=27)

· Risk depends on size of inserted segment and viability of the partial trisomies and monosomies produced

· Unbalanced offspring typically have either a pure partial monosomy or a pure partial trisomy

· Interchromosomal:

· Theoretical risk of 50% of producing a conceptus with an unbalanced karyotype

· Risk for an abnormal liveborn child depends on the viability of the partial trisomy or partial monosomy of the inserted segment

· Overall risk 32% for a male carrier, 36% for a female carrier

· Interchromosomal, long segment:

· May form quadrivalent

· Recombinant chromosomes would have duplications and deletions

References:

· Gersen SL, Keagle MB. The Principles of Clinical Cytogenetics. 2nd ed. Humana Press; 2004:616.