The differential diagnosis of cyst-like cortical defects in children included unicameral bone cyst, nonossifying fibroma, an eosinophilic granuloma, osteomyelitis, cystic bone tumors, and transient cyst-like cortical defects.2, 8 Osteomyelitis was excluded in our patient based on clinical absence of signs of inflammation and normal WBC count and CRP. This evidence concerns the gene CRP and cyst.