Speckled lentiginous nevus syndrome, a so far unrecognized cutaneous phenotype associated with neurological anomalies, is postulated on the basis of the following arguments. Phacomatosis pigmentokeratotica represents a twin spot phenomenon. One isolated half of this complex phenotype is observed rather often in the form of Schimmelpenning syndrome, whereas the other half of this twin nevus syndrome consists of a speckled lentiginous nevus associated with various neurological abnormalities incompatible with Schimmelpenning syndrome, such as hyperhidrosis, muscular weakness and dysesthesia. This second component of phacomatosis pigmentokeratotica may likewise occur separately. For the association of speckled lentiginous nevus with hyperhidrosis, muscular weakness, dysesthesia or other neurological abnormalities, the term "speckled lentiginous nevus syndrome" is proposed. Some case reports that may be categorized as examples of this new syndrome are reviewed. The postulated new phenotype is tentatively categorized as a paradominant trait. Future clinical studies will probably confirm the existence of speckled lentiginous nevus syndrome as a distinct neurocutaneous phenotype.