** Thanks for contacting with your health concern 1. Since he was diagnosed at birth, thus attending doctor/Pediatrician must have excluded most of the differential diagnosis before arriving at epidermus nevus 2. As you judged correctly: as the age progress, the nevi can become thicker, darker and can be flat, tan or brown patches of the skin. PS. keep in mind that people with nevus epidermis also have extracutaneous abnormalities affecting the brain, eyes or bone [epidermal nevus syndrome], so check with - neurological [brain] abnormalities like cognitive abnormality, developmental delays. - skeletal [bone] abnormalities like abnormal curvature of the spine, any abnormality of arms and legs. - Ocular [eyes] abnormality may include cataract, opacity of the cornea. - Vitamin D resistant rickets [can also occur] PS. thus child should be under the regular supervision of Pediatrician, pediatric neurologist, ophthalmologist, orthopedic surgeon to systematically and comprehensively plan child treatment.