Background. Forearm fractures are the most frequent fractures in children and adolescents and they are more common in males than in females. In the last 20 years the increase of surgical indications have resulted in more complications, among them the non-unions, considered extremely rare and severe in children, have increased in incidence. We report a successful treatment of misdiagnosed forearm atrophic non-union with severe osteolysis using fibula allograft and autograft growth factors in a previously healthy 4-year-old child. Clinical case. A 4 year-old boy presented to our hospital with massive bone loss and a negative bone biopsy for Gorham-Stout Syndrome, he also showed reactive bone tissue with abnormal vascularity, necrotic osteocartilaginous fragments and giant mononucleated cells. Other lab tests did not show any modifications, so all the causes of paediatric osteolysis were ruled out. He had already undergone a few surgeries on that fracture and we performed others before achieving a good result, obtained with an autologous fibula graft with medullary growth factors stabilized with Kirschner wire. At the follow up 28 months later, the patient showed total consolidation of the initial area of non- union, no neurovascular deficit and no joint deficiency. Discussion. Non-union in paediatric patients is rare and therefore difficult to treat and diagnose. Since all of our tests ruled out the main causes of paediatric non-union, we managed the case with strategies usually applied to adult patients, carefully respecting the growth plates. Conclusion. Although this is a single-case report, it underlines the importance of early diagnosis, the difficulty to rule out some pediatric causes of bone loss and the complicances of a wrong diagnosis/treatment. It also shows that the use of allograft bone and autograft growth factors in a pediatric patient, who has undergone multiple surgeries, can lead to excellent results