Clinical and Radiological Improvement in Gorham-Stout Disease after Sirolimus Treatment

Background: Gorham-Stout disease (GSD) is a rare syndrome characterized by lymphatic malformations, mainly in bone structures, causing progressive osteolysis. Lymphatic endothelial cell proliferation depends on several growth factors that use the phosphoinositide-3 kinase (PI3K)/Akt pathway and converge on the mammalian target molecule of the rapamycin (mTOR) pathway. These findings have allowed treating GSD with mTOR pathway inhibitors such as sirolimus or everolimus. Case report: We present the case of a one-year-old female patient referred to our institution after a right femur fracture and progressive limb volume increase, disproportionately to the trauma. After several episodes of soft tissue infections, imaging studies showed pseudarthrosis, lytic lesions, and progressive loss of the right femur that ended in total absence. A femur biopsy showed lymphatic structures positive with D2-40 staining, diagnosing GSD. After six months of non-response to traditional treatments, the limb was disarticulated at the hip level, and oral sirolimus treatment was initiated, showing clinical and radiological improvement with minor lytic lesions and evidence of ossification after 20 months of treatment. Conclusions: Oral sirolimus treatment for GSD inhibits angiogenesis and osteoclastic activity, stimulating bone anabolism and leading to arrested osteolysis progression and improved ossification, quality of life, and patient prognosis. Therefore, sirolimus should be considered a therapeutic option for this rare disease.