Table 4.

Diagnostic criteria for mosaic Legius syndrome.

The diagnostic criteria for mosaic Legius syndrome are met in an individual if any of the following is present:

1. A heterozygous pathogenic SPRED1 variant with a variant allele fraction of significantly less than 50% in apparently normal tissue such as white blood cells AND six or more café-au-lait macules

2. An identical pathogenic heterozygous SPRED1 variant in two independent affected tissues (in the absence of a pathogenic SPRED1 variant in unaffected tissue)a

3. A clearly segmental distribution of café-au-lait macules AND a child fulfilling the criteria for Legius syndrome

^aDifferent tissues originating from the same primary affected lesion count for one tissue only.