CASE 1

BY Dr. NIZAR AL-NAKSHABANDI MD, FRCPC

HISTORY: 46-year-old complaining of shoulder pain.

What are your findings?

What is the differential diagnosis?

What are the causes?

FINDINGS:

An X-ray of the foot was ordered to assess disease extent and it demonstrated diffuse osteopenia with permeative lytic appearance. Diffuse soft tissue swelling with obliteration of the Kager’s fat pad.

Sagittal CT of foot show avid FDG uptake at the tarsal bones and with in the soft tissues.

Coronal STIR, mid foot show bone marrow edema with dot in a circle sign.

DIFFERENTIAL DIAGNOSIS:

• Madura’s foot.

• Osteomyelitis.

• Septic arthritis.

DIAGNOSIS:

Madura’s foot.

PEARLS AND DISCUSSION:

Mycetoma is a chronic and progressively destructive skin infection, that may affect subcutaneous tissues, fascia, muscle, and bone after localized trauma, usually but not invariably to the foot, Injury could either introduce fungi (eumycetoma) or aerobic actinomycetes (actinomycetoma). It produces localized swelling and contains suppurative granulomas with multiple sinus tracts extruding macroscopic colored granules. In nocardiosis, mycetoma is the only clinical form that is associated with granules.

Nocardia species are aerobic actinomycetes mostly happening in immunocompromised patients. However, up to one-third of patients with nocardiosis are immunocompetent N. transvalensis (Nocardia transvalensis) is a rare pathogen that appears to behave clinically like other Nocardia species. Osteomyelitis is a common complication, and plain X-ray assessment or CT scan is advisable to demonstrate bony osteolytic areas and eventual periosteal reaction. The initial radiographic changes include periosteal reaction, new bone formation, and cortical erosions. This then progresses to remarkable sclerosis, lytic lesions (geodes), and osteopenia secondary to disuse. The “dot-in-circle” sign has been a highly specific early sign of mycetoma on magnetic resonance imaging (MRI). Piper et al. reported the first case of N. transvalensis infection in 1927 as a pathogen of foot mycetoma in a South African patient. It has since been reported in a range of other infections in Australia, Africa, North America, Europe and Thailand with a few reported in Japan and Saudi Arabia.

FURTHER READING:

1. Al-Hajjar Y, Al-Nakshabandi N. Nocardia transvalensis/wallacei hindfoot actinomycetoma, International Journal of Diagnostic Imaging, 2016, Vol. 3, No. 2. September 2016.

2. Hamid ME, Al Azraqi TA, Joseph MR, et al. Isolation of a rare Nocardia wallacei from an HIV-positive patient with pulmonary infection in southern region of Saudi Arabia. Saudi Medical Journal. 2013; 34(6): 644-7.

3. Parker L, Singh D, Biz C. The dot-in-circle sign in Madura foot. The Journal of Foot and Ankle Surgery. 2009; 48(6): 690-e1. PMid:19857827