Diagnosis of the autosomal dominant syndrome--which results from a neurofibromin defect and occurs in 1 of 2,000-4,500 individuals--requires the presence of two or more of the following diagnostic criteria: six or more CALMs greater than 0.5 cm in diameter in prepubertal children, or greater than 1.5 cm in those postpubertal; two or more neurofibromas of any type, or one plexiform neurofibroma; axillary and/or inguinal freckling (Crowe's sign
); optic glioma; two or more Lisch nodules; a bony lesion (such as sphenoid dysplasia or long bone dysplasia); and a first-degree relative with NF1.
Children with neurofibromatosis type 1 may demonstrate Crowe's sign
(axillary freckling); but their plexiform neuromas, if present, may contain significantly more pigment than lesions pictured in textbooks.
According to the 1988 National Institutes of Health Consensus Development Conference, a diagnosis of NF1 requires two or more of the following clinical features: six or more cafeau-lait macules, two or more neurofibromas or one or more plexiform neurofibromas, freckling in the axilla and inguinal region (Crowe's sign
), tumor of the optic nerve pathway, two or more Lisch nodules (iris hamartomas), and distinctive osseous lesions.