Background
Myositis ossificans circumscripta (MOC) is a non-neoplastic, localized, and self-limiting soft-tissue tumor and is associated with prominent heterotrophic bone formation within the muscles, ligaments, and fascia (1). About 60 to 75% of all cases are due to trauma (2). MOC commonly affects young people but is rare in children and older patients (3). Men are more commonly affected than women during their second and third decades of life (3,4).
Though it can occur in any body part, MOC lesions are commonly found at sites most prone to injuries which are large muscles of the extremities (5). Myositis ossificans arising from the abdominal muscles is extremely rare, and if it appears, it tends to arise from abdominal operation scars (3,6). MOC can be hereditary or non-hereditary (7,8). The hereditary form (myositis ossificans progressiva) is due to an overexpression of bone morphogenetic protein 4(BMP4) mapped to chromosome 14 (9,10). The non-hereditary type is a commonly post-traumatic and well-defined lesion that usually complicates the hematoma of the affected muscles (2,11). The signs and symptoms are specific and they can be confused with malignant lesions, such as osteosarcoma and soft-tissue sarcoma (12). Radiological imaging is crucial for excluding infections or malignancies and in the diagnosis of myositis ossificans (13). The diagnosis of myositis ossificans can be confirmed by histology (8,14). Herein, we present histology confirmed non-traumatic MOC of the anterior abdominal wall in a seven years old Ugandan male.