Hi, welcome to the ehealth forum and I am glad to help you.
You seem concerned by the hair loss at the age of 16 years having lost half the hair volume over the last year. You have also mentioned scaly bumps which progress to scab like things.
Tinea Capitis is an important reason why some teenagers experience hair loss. This condition is also known as scalp ringworm, which is a fungus that can cause hair to be lost in patches, hair to be broken, and the scalp to be affected. Tinea Capitis is contagious, therefore be certain to treat it with anti-fungal shampoos immediately upon discovery in consultation with your dermatologist.
Other causes of hair loss include alopecia areata and traction alopecia.
Hope this helps. Take care.
Note: This post is for patient education only and no specific diagnosis is claimed thereby.