Infantile myofibromatosis (IM) is rare and often enigmatic. We present the case of a 4mo ex-33-week male with a history of twin-twin transfusion syndrome, recurrent intussusception, rectal prolapse, and pancreatic insufficiency who was transferred to our hospital for persistent failure to thrive. Initial radiograph shortly after transfer revealed focal lytic lesions in the proximal bilateral femurs. This prompted a review of a CT done 2 months earlier at an outside hospital which revealed subtle mildly expansile lytic lesions within the ribs, iliac bones, and proximal femurs. On follow up CT and MRI at our hospital, these lesions had increased in size and number with newly apparent multilevel thoracolumbar spinal lesions with associated fractures. There was also bowel wall thickening and new hepatomegaly, suggestive of visceral involvement. Biopsy of a lesion in the left tibia was consistent with infantile myofibromatosis. After treatment with vinblastine/methotrexate and imatinib, CT demonstrated decrease in extent of osseous lytic disease, improvement in bowel wall thickening, and reduced hepatomegaly. About 90% of IM cases occur within the first two years of life and are subdivided into three categories: 1. solitary (50-80% of cases); 2. multicentric without visceral involvement; or 3. Generalized/multicentric with visceral disease. The most commons sites of solitary disease are the head/neck or trunk, and multicentric disease typically involves additional regions of skin/subcutaneous tissue, muscle, or bone (skull, femur, tibia, spine, ribs). One third of multicentric IM also manifests with visceral involvement, or generalized IM, like in this patient with osseous as well as bowel/visceral involvement. Though most cases are sporadic, IM can also rarely be familial. Though solitary and multicentric IM are considered benign and typically regress over 1-2 years, visceral involvement in generalized IM is associated with poor outcomes with reported mortality rates as high as 76%; it is usually treated with chemotherapy, as done here. Radiologist suspicion is critical for diagnosis, as in this case with the lytic bone lesions on radiograph. Imaging detection is thus also critical for accurately describing the extent of disease and to help direct treatment. With variable imaging findings described in past reports, we elucidate the imaging characteristics of IM seen on radiography, CT, MRI, and ultrasound. Read More

Meeting name: SPR 2025 Annual Meeting , 2025

Authors: Ocal Selin, Tivnan Patrick, Alizadeh Houman

Keywords: Musculoskeletal, Multimodality Guidance, Rare Neoplasms