Preferred test to confirm Legius syndrome for symptomatic individuals who test negative for NF1 gene variants.
Polymerase Chain Reaction/Sequencing/Multiplex Ligation-dependent Probe Amplification
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
Transport 3 mL whole blood. (Min: 2 mL)
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Background Information for Legius Syndrome (SPRED1) Sequencing and Deletion/Duplication:
Characteristics: Cafe au lait spots, axillary and inguinal freckling, learning disabilities and macrocephaly. Neurofibromas, lisch nodules and CNS tumors are not observed.
Incidence: Unknown; may represent 0.5 percent of neurofibromatosis type 1 diagnoses or 8 percent of those with isolated cafe au lait spots.
Inheritance: Autosomal dominant.
Cause: Pathogenic SPRED1 gene mutations.
Clinical Sensitivity: Unknown.
Methodology: Bidirectional sequencing and multiplex ligation-dependent probe amplification (MLPA) of the entire coding region and intron-exon boundaries of the SPRED1 gene.
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations and deep intronic mutations will not be detected. Deletion/duplication breakpoints will not be determined.
Laboratory Developed Test (LDT)
|Component Test Code*||Component Chart Name||LOINC|
|2008348||Legius Syndrome (SPRED1)Seq, DelDup Spcm|
|2008349||Legius Syndrome (SPRED1)Seq, DelDup Int|
- SPRED1 sequencing and deletion/duplication