RESUMEN
Here we describe the results obtained in a sample of 209 Brazilian patients affected by neurofibromatosis type 1 (NF1 or von Recklinghausen´s disease). The phenotypic description of the sample included the determination of average values and frequency estimates of 25 measurements, signs, and symptoms according to their occurrence (familial or isolated) and to sex and age. The following parameters were estimated from our sample: proportion of familial and isolated cases, sex-ratio, segregation rate, penetrance value, fitness value, and birth order effect. We studied also the pattern of distribution of skin pigmentation spots and neurofibromas and determined the conditional probabilities favoring the diagnosis of NF1 of primary and secondary signs and symptoms presented by adults suspected of having the condition.