.Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis, characterized by unknown aetiology and sterile neutrophilic infiltrate on histological examination, clinically showing recurrent skin ulcers and mostly affecting lower limbs areas. In 2/3 of the cases, PG is secondary to another disorder such as inflammatory bowel and lymphoproliferative diseases, infections, rheumatic diseases and auto-inflammatory syndromes. The paper describes the cases of three paediatric patients showing the association of PG with rheumatic conditions such as Behçet’s disease, chronic recurrent multifocal osteomyelitis (CRMO) and PAPA (Pyogenic Arthritis, Pyoderma gangrenosum and Acne) syndrome and proposes a diagnostic flow-chart to help paediatricians recognize PG and associated conditions.