The diagnosis of neurofibromatosis type I (NF1) has traditionally rested upon the presence of certain clinical features, including café-au-lait macules and freckling on the skin, and a variety of tumours, particularly neurofibromas. Skin changes are often the earliest manifestation, and therefore of particular significance when assessing people at risk of NF1. A rare, atypical, form of NF1 with few skin features and a predominance of spinal neurofibromas is known. Five affected families, in whom skin features were absent or very mild, were identified. Many affected individuals had severe pain and poor mobility from spinal tumours. Because of the lack of skin features, their diagnosis was often delayed, emphasising the importance of genetic testing for this condition. (By Dr Emma MM Burkitt Wright, http://jmg.bmj.com/content/50/9/606 )