Summary section

Causes of Cornelia de Lange Syndrome recommendations:

R4: Classic CdLS is usually caused by variants in NIPBL; however, variants in one of six other genes – SMC1A, SMC3, RAD21, BRD4, HDAC8 or ANKRD11 – should also be considered, as they may lead to a similar phenotype.

R5: Mosaicism should be considered in individuals with CdLS in whom a variant in a gene known to cause CdLS cannot be detected in blood cells, in which case other tissues such as fibroblasts (skin), buccal (cheek) cells or bladder epithelial cells from urine should be studied.

R6: Genetic counselling should be offered to all families with a family member with CdLS. Families should be counselled that the recurrence risk of CdLS differs depending on the gene involved. In the non-X-linked forms, the recurrence risk is 0.89% due to germline mosaicism. Autosomal dominant inheritance of CdLS does occur, meaning if one copy of the mutation is present, the individual will show clinical effects. In clinically diagnosed individuals with CdLS, the recurrence risk is 1.5%.

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