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A 5-year-old male with a painless lump on his right proximal thigh
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A 5-year-old male was brought to his primary provider for evaluation of a slowly growing, painless lump in the patient’s right proximal thigh. The problem was first noted a few weeks earlier but may have been there longer, and it appears to be slowly growing in size. The diagnosis of impetigo was made, and the patient was given a prescription for cephalexin (Keflex, Flynn Pharma) without improvement. It was soon noted that there was some intermittent discharge of a small amount of clear fluid from the center of the lesion (Figure 1). The material was swabbed and sent for Gram stain and culture, and a course of clindamycin was given. Both the Gram stain and culture were negative, and the clindamycin had no benefit.
Source: James H. Brien, DO
The patient is otherwise healthy, with no significant past medical illnesses, injuries or suspicion of immunodeficiency. However, he is a typical 5-year-old male who has numerous minor injuries to his lower extremities with numerous breaks in the skin of the lower legs (Figure 2). The parents cannot remember any specific injury of the area of concern, but according to his parents, considering his activities, an injury in that area would not be unusual. His immunizations are up to date, with no injections in his thighs since he was around 2 years of age.
Examination reveals normal vital signs, and normal growth and development. The only abnormal finding is a soft mass in the right proximal, medial thigh, measuring about 2 × 2 cm, with some dark erythema about the lesion, as well as the umbilicated or puckered apex of the lesion, as noted in the figure above. The rest of the exam is normal.
A chest radiograph was clear and a tuberculin skin test (TST) developed a reaction measuring 5 × 5 mm induration. A subsequent interferon-gamma release assay (T-spot) was negative. The patient had surgical drainage of several milliliters of pus (Figure 3). Gram and fungal stains were negative, but the acid-fast stain (AFB) was positive for Acid Fast bacilli.
What’s your diagnosis?
A. Nontuberculous mycobacteria infection
B. MRSA lymphadenitis
C. Sporotrichosis
D. Cutaneous nocardiosis
Case Discussion
The AFB culture grew Mycobacterium avium-intracellularae complex (MAC), a common nontuberculous mycobacteria (A). The patient was treated with 6 weeks of oral clarithromycin plus rifampin with complete healing. It was thought at first that this must be lymphadenitis of a femoral node, but it appeared at surgery to be a soft tissue infection with an abscess, probably from inoculation with an injury many weeks earlier. This organism is by far the most common cause of nontuberculous mycobacteria infection of cervical lymph nodes (Figures 4 and 5), but it is very uncommon to see an infection elsewhere in the normal, immunocompetent host, which is somewhat surprising, considering that the organism is very ubiquitous in the environment, even occasionally found in common tap water. Primary soft tissue infections by inoculation with other nontuberculous mycobacteria, such as M. marinum are well-recognized. Other species, such as M. fortuitum (Figures 6 to 9) can also be seen causing soft tissue infections. But, MAC is a very uncommon cause of soft tissue infection and abscess formation.
Treatment of these organisms is often curative by surgery alone. When medical treatment is used, it is best for it to be based on sensitivity testing, and usually includes a macrolide, such as clarithromycin, usually in combination with rifampin for 6 to 12 weeks.
For an excellent review of nontuberculous mycobacteria, I would recommend Chapter 135 in Sarah Long’s 5th Edition of Principles and Practice of Pediatric Infectious Diseases, pages 806 to 812, by Marc Tebruegge and Nigel Curtis, both of the University of Melbourne, Australia.
Both lymphocutaneous sporotrichosis (Figure 10) and cutaneous nocardiosis (Figure 11) can also occur as a result of primary inoculation. Sporotrichosis may take weeks to confirm by culture (the gold standard), but fungal staining of biopsy tissue may revel typical cigar-shaped yeast, supporting the diagnosis in the proper setting. Likewise, serologic testing may be supportive but not very reliable. The recommended treatment is Itraconazole for 3 to 6 months. For a severe infection, amphotericin B is recommended.
A tissue biopsy of an area of Nocardia infection will reveal AFB-positive organisms, but rather than bacilli, they will be thinner, filamentous rods (Figure 12, courtesy of James W. Bass, MD). The patient in Figure 11 was a young child who presented with a cluster of superficial lesions as shown on the buttock area. It was initially thought to be common impetigo and was cultured prior to starting treatment. The lab called a couple of weeks later to let me know that a Gram-positive filamentous rod was growing, and was subsequently identified as Nocardia. In the meantime, treatment was changed to trimethoprim-sulfamethoxazole therapy for about 6 weeks, with clearance of the lesions. Severe infections may require 6 to 12 months of treatment. In retrospect, the child was thought to have acquired the infection from playing in a sand box, although soil is usually the source of Nocardia infections.
An old friend, Ted Eickhoff, MD, died March 24 at 86 years of age. Most readers will not know who he was. Ted was the founding Chief Medical Editor of Infectious Disease News, which began July 1988. It is the “adult” version of Infectious Diseases in Children, which also began that same year with Phil Brunell, MD, as the Chief Medical Editor. It was Ted’s vision to begin this column, and he recruited me to write it for Infectious Disease News, with the first column appearing in the December 1988 issue. Soon, Dr. Brunell had me doing the same column in this publication as well, starting with the April 1989 issue, and obviously, continuing today. Without Ted, it is unlikely this column would exist, at least not with me writing it. So, my thanks and sympathies go out to the Eickhoff family. He was truly a gentleman and a scholar, to whom I owe a great debt of gratitude.
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- James H. Brien, DO, is an adjunct professor of pediatrics with the section of infectious diseases at McLane Children’s Hospital, Baylor Scott & White Health, Texas A&M College of Medicine in Temple, Texas. He also is a member of the Infectious Diseases in Children Editorial Board. Brien can be reached at: jhbrien@aol.com.
Disclosure: Brien reports no relevant financial disclosures.