Penetrance, expressivity, mosaicism, and anticipation
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A 28-year-old woman seeks counseling after her infant daughter is found to carry the family's pathogenic NF1 variant. The woman has café-au-lait macules, axillary freckling, and a few cutaneous neurofibromas but no visual or skeletal complications. Her brother carries the same constitutional variant and has required treatment for an optic pathway glioma and severe scoliosis. She asks whether her own mild course predicts the daughter's future manifestations.