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.