Neurofibromatosis: a neoplastic birth defect with two age peaks of severe problems.

A survey involving more than 400,000 patient sources revealed a population of 129 NFT patients relatively unbiased by the specific character of the disease (eg neurologic vs orthopedic problems), though biased in terms of severity. Two age peaks of severe disease were demononstrated, one early in life (10 yr or less) and one late (apex in 36- to 50-yr group). Neural crest-derived malignancies were the critical component of the second peak (75% of severe cases). The high burden nature of the disorder is emphasized by the fact that moderate and severe cases amounted to 64% in the survey population (ie those brought to medical attention) and 26% in nonproband affected family members in 46 families. In addition, even correcting for 5% of ascertainment of minimal-mild cases and 61% ascertainment of moderate-sever cases, 7% of the presumed NFT population may be considereed at risk for severe problems.