My 11yr old daughter is all of a sudden losing hair. clumps of it will come out. she suffered from hsp in 2015, could it be related?

Alopecia areata: patchy hair loss can occur in young female adults. Its etiology is unknown. Trichotillomania can also occur with a person pulling out their own hair. Alopecia can result in total baldness, or partial. The hair may regrow over time. telogen effluvium can occur where in a young developing adult, their hair may change groth cycles and result in partial baldness.

Technically, no, this would not be a part of Henoch-Schönlein purpura (HSP). However, it could be alopecia areata which is also an autoimmune condition like HSP. Make sure your daughter's dermatologist knows about her previous HSP. There are other causes of hair loss so a work-up is needed.