What is a nevus? Nevus (also spelled naevus; plural nevi) in the broad sense, means birthmark. There are several types of nevi: epidermal, melanocytic and connective tissue nevi. Melanocytic means that it is pigment-based. Congenital means it is present at birth.
Nevi are the most common abnormality of the skin. They apparently serve no function. Normally, skin gets its color from melanin, which is produced by cells called melanocytes. Melanin is human pigment. Normally, melanin is distributed fairly evenly throughout the skin. Congenital melanocytic nevi, on the other hand, are made up of pigment-producing cells called nevomelanocytes. These cells are not evenly distributed. When many nevomelanocytes are clumped together, they can result in moles on the skin because of the higher concentration of melanin (pigment).
Joshua's nevus looks like this:
You've probably never even noticed Joshua's nevus. We've been really good about the kids wearing hats when outdoors. And his hair covers it so well, it's never been something that peole have noticed. To us (and everyone) he is just Joshua. And we love our Joshua.