Mumps is very common in small children and usually doesn’t cause any long term problems. However, it is more of a problem for teenage boys and young men who run the risk of contracting orchitis.
Orchitis is a painful inflammation of the testes which can affect one of both testicles. Treatment involves painkillers, bed rest and a support bandage if necessary.
It can cause shrinkage of the testicle in a few rare cases but most cases respond well to treatment.
Very few cases result in infertility but it’s worth mentioning this to your GP or fertility specialist.