What the percentage of person who has cafe au lait spots gets neurofibromatosis?

Number of spots. Many people who do not have nf have a few café-au-lait spots . If a young child has five or more, at least ½ inch or 15 mm in size post puberty lookfor other signs such as neurofibromas — tumors along skin and lisch nodules, tiny, noncancerous tumors on the iris (the colored part of the eye). Consult physician to better assess individual signs for diagnosis.
77% if >6 CALMs. A 2009 study in archives of dermatology showed 34/44 (77%) of children under age 3 who had 6 or more cafe au lait macules (calms) were eventually diagnosed with neurofibromatosis 1 (nf1). The average # of calms for children who were not diagnosed with nf1 was 5, but 12 for those who were diagnosed with nf1. One or two calms does not mean someone has nf1.