The authors report the case study of a 13-year-old girl, suffering from epigastric pain related to an important infectious syndrome and from marked hypertrophic pneumosteopathy (clubbed fingers, diffuse cortical hyperostosis). Radiological examination (chest x-ray and computed tomography scan) showed a partly calcified right posterior mediastinal mass. The esophagoscopy showed a fistular emanation from the esophagus to the tumor. The biopsy results were of no diagnostic significance, and the samples demonstrated a bacterial and fungal colonization. An endoscopic sonogram showed an inhomogeneous mass with hyperechoic structures developed between the mucosa and the outer muscular coat of the esophagus. The patient underwent surgery, which showed a large intraparietal tumor of the esophagus, which, through pathological examination, was confirmed to be a benign leiomyoma. Postoperative follow-up was simple and the pneumosteopathic symptoms regressed rapidly. This disease is rare in children under 15 years of age. It is only exceptionally associated with a hypertrophic pneumosteopathy. This pathology is diagnostically challenging to the surgeon. The endoscopic ultrasonography is the best procedure in the assessment of subepithelial tumor and extrinsic compressions of the oesophagus.