The co-existence of papular nevus spilus (PNS) and ipsilateral extracutaneous abnormalities involving peripheral nerves of the skin or muscles was originally described as \"speckled lentiginous nevus syndrome\". To avoid confusion with macular nevus spilus, the condition was recently re-named \"papular nevus spilus syndrome\". In addition to 14 published cases, we identified six new cases via a search of the worldwide literature. New diagnostic criteria are suggested: (1) presence of a PNS; (2) presence of a neurological or skeletal abnormality which is usually ipsilateral to the nevus; and (3) absence of a nevus sebaceus. According to current knowledge, PNS syndrome is a rather rarely occurring, sporadic disorder that can be considered to be part of a spectrum of mosaic RASopathies, which includes isolated PNS, isolated nevus sebaceus, PNS syndrome, Schimmelpenning syndrome, and phacomatosis pigmentokeratotica.

Speckled lentiginous nevus syndrome has been described in individuals with a speckled lentiginous nevus with rare associated neurologic deficits. Because speckled lentiginous nevus syndrome almost always affects adults, it is not typically considered when evaluating children. We present the first reported case of speckled lentiginous nevus syndrome presenting in a young child with muscle atrophy and motor deficits affecting muscles along the same distribution as the speckled lentiginous nevus.