It can be due to keratosis pilaris, pemphigus or linear pororkeratosis (if arranged around a particular dermatome). I suggest you to consult a dermatologist and get a biopsy skin done to confirm the diagnosis.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Possibly 'Linear Porokeratosis' from your descriptions. This occurs by birth.Treatment might be with calcipotriol creme (A dermatologist prescription only)