This is a commonly used mnemonic to recall the differential diagnosis for periosteal reactions in children:

P – physiologic, prostaglandin therapy

E – eosinophilic granuloma

R – rickets

I – infantile cortical hyperostosis

O – osteomyelitis

S – scurvy

T – trauma

E – Ewing Sarcoma

A – hypervitaminosis A

L – leukemia

S – syphilis

O – osteosarcoma 

C – child abuse 

K – kinky hair syndrome

S – sickle cell disease