Hello! Common possibilities may include ringworm or a superficial (surface) bacterial infection. Neither are likely to occur spontaneously. Bacterial or yeast infection can occur following inflammation or allergy which weaken the skin's normally superb defences. Ringworm pops up where dogs have been in contact with sufferers, especially in cases where the pet has a weakened or vulnerable immune system (sometimes by virtue of the very fact they are young). There are certainly other causes of skin disease that I can't rule out from here (eg underlying diabetes / cancer / parasites etc) so a vet appointment would definitely be advisable. Normally, vets try to address the cause and treat the symptoms together. Best of luck - and please do let us know how you get on!