Hello and welcome to HCM

Vitiligo is an autoimmune disease. It can appear at any age.
However, every white/ depigmented patch on body is not due to vitiligo.
There are various other causes of white patch on body, namely:
1. skin conditions like eczema, psoriasis
2. Fungal infections
3.Vitamin defiency (Vitamin B 12 deficiency)

You have given the history that the white patch is present at the site where the baby vomits after breast feeding.
So there is a possibility that the patch could be due to maceration of skin.
Wetting of skin for long and contact with gastric juices in the vomitus can cause the maceration to baby's delicate skin.

Keep the skin clean and dry in that area.
If it does not resolve you need to visit your doctor.

Thanks and take care
Dr Shailja P Wahal

Hello. Welcome to Healthcare Magic. I'm Dr. Christensen.
Vitiligo is caused by an immune reaction to the pigment cells in a person's skin. It can occur as an isolated phenomenon -- that is, it can occur when there are no other autoimmune diseases present -- or it can be part of another autoimmune disorder, such as type 1 diabetes or rheumatoid arthritis.
According to the American Vitiligo Research Foundation, most cases of vitiligo develop in individuals between the ages of 10 and 30 years, but it can occur in infants, too. In fact, some babies are born with vitiligo. Family history is one risk factor for vitiligo, but an infant can develop vitiligo when other family members don't have the condition.
Now, if there has been some inflammation and exfoliation on this baby's neck, this may not be vitiligo at all. Inflammation can temporarily lead to blanching or darkening of the skin. Blanching due to inflammation is called post-inflammatory hypopigmentation, while darkening is called post-inflammatory hyperpigmentation. Such changes in skin color due to inflammation can last for several weeks to several months, and occasionally they are permanent.
Since it isn't possible to diagnose a skin disorder without an examination, this baby should be seen by his or her pediatrician to determine the cause of these pigment changes.
I hope that answers your question.

vitiligo can appear in newborn babies.it is congenital vitiligo. there is genetic predisposition in occurrance in 30% of cases where family history is ab=vailable. but in other cases there is no family history . this lesions may occur after local trauma and inflammation and excoriation of the area. it can be differentiated by skin biopsy.