Case 249: Intramuscular Mycetoma

Spinal Eumycetoma: A Rare Cause of Lumbar Canal Stenosis and Significance of "Dot in Circle"

Mycetoma is a chronic granulomatous disease that is more common in tropical regions with predominant involvement of foot. Spinal mycetoma presenting as lumbar canal stenosis is extremely rare. We hereby present a case of fungal eumycetoma of vertebral column in a 42-year-old male who presented with chronic progressive low back pain and features of lumbar canal stenosis without any skin swelling or discharging sinuses. The “dot-in-circle” sign, a highly specific magnetic resonance imaging (MRI) and ultrasonography (USG) sign of mycetoma has been described in the literature as a pathognomonic feature of mycetoma involving the musculoskeletal system. We describe the importance of characteristic imaging features with dot in circle sign in the diagnosis of eumycetoma of lumbar spine.

Soft tissue mycetoma: "Dot-in-circle" sign on magnetic resonance imaging

A 36-year-old Mexican female with a slowly growing foot mass was referred to orthopedic surgery clinic for further evaluation. Foot magnetic resonance imaging revealed an infiltrative soft tissue mass along the dorsal aspect of the fourth metatarsal. T2-weighted images revealed multiple central low-signal “dots” surrounded by areas of bright signal intensity, known as the “dot-in-circle” sign, which is highly specific for mycetoma. Surgical biopsy confirmed the diagnosis of bacterial mycetoma in this patient. Mycetoma can lead to progressive deformity and loss of function, as well as possible limb amputation in the case of delayed diagnosis or misdiagnosis. The “dot-in-circle” sign on magnetic resonance imaging can assist in rendering a final diagnosis and distinguish mycetoma from other etiologies of a soft tissue mass, such as a sarcoma or benign soft tissue lesions.