A 5-year-old Hispanic girl presented with an 18-month history of nonhealing, slightly painful, firm, 1- to 4-cm plaques on her left arm, and a sinus draining serosanguineous fluid. She had been living in Mexico at the time of onset and had no history of trauma, fever, cough, or weight loss. What's your diagnosis?
SAN DIEGO — Differential diagnoses included cutaneous tuberculosis, mycetoma, leishmaniasis, botryomycosis, coccidioidomycosis, osteomyelitis, bone and soft tissue tumors, and other deep fungal or atypical mycobacterial infections.
Diagnostic tests—including complete blood count, chemistry panel, and x-rays of the chest and left arm—were all negative.
Skin biopsy revealed a suppurative granuloma with deeply basophilic granules in the dermis. Gram stain revealed gram-positive branched bacteria. Culture was diagnostic for actinomycetoma, as it grew Nocardia brasiliensis, Dr. Justine Hyoju Yun said at the annual meeting of the Society for Pediatric Dermatology.
First-line treatment for actinomycetoma is 5-10 mg/kg per day of trimethoprim and 25-50 mg/kg per day of sulfamethoxazole in two to four divided dosages. Immunocompetent patients should be treated for 3 months, and immunocompromised patients should be treated for 6 months.
Dr. Yun's patient was started on 160 mg oral trimethoprim and 800 mg oral sulfamethoxazole daily in two divided doses for 3 months. She has responded well to treatment, with residual atrophic pink plaques on physical exam.
Mycetoma is a chronic, granulomatous infection of the skin and subcutaneous tissues caused by either bacteria or fungi. Untreated, it can spread locally to adjacent muscle and bone.
Firm, painless nodules usually appear on the foot, but also may affect the hands, arms, chest, and buttocks. Tubercles and draining sinuses may develop, as well as ulceration and scarring.
Actinomycetoma is caused by actinomycetes, whereas eumycetoma is caused by fungi. They are clinically indistinguishable but are treated differently. Causative microorganisms include the Actinomadura species, Nocardia species, and Streptomyces species. N. brasiliensis is implicated in 98% of cases in Mexico, said Dr. Yun, a dermatology resident at King/Drew Medical Center, Los Angeles.
In the West, mycetoma is most common in Mexico, followed by Venezuela and Argentina. It affects males more often than females (5:1).
Left untreated, mycetoma can spread locally from skin to subcutaneous fascia and bone.
Culture and biochemical testing are necessary to identify the causative agent, as this determines treatment. However, Nocardia species are difficult to culture and can take up to 3 weeks to grow.
Photos courtesy Dr. Justine Hyoju Yun