DefinitionA congenital pigmented or melanocytic nevus is a dark colored, often hairy patch of skin that is present at birth.Smaller in infants and children, they usually continue to grow along with the child. A giant pigmented nevus is larger than 8 inches once it stops growing.Alternative NamesCongenital giant pigmented nevus; Giant hairy nevus; Giant pigmented nevus; Bathing trunk nevus; Congenital melanocytic nevus - largeCauses, incidence, and risk factorsBathing trunk nevi are thought to be caused by defects or problems that occur as a baby grows in the womb. However, in some families bathing trunk nevus may be inherited.Bathing trunk nevus may occur with:Growth of fatty tissue cells (lipomas)NeurofibromatosisOther neviSpina bifidaSmaller congenital pigmented or melanocytic nevi can b