A 79-year-old woman presented to her primary care physician in May 2005 with a "spider bite" that began as two lesions on her forearm near her elbow, sustained three weeks previously in Hawaii. After 10 days on Keflex, the raised, erythematous to purple skin changes were still evident, and seven additional lesions had appeared distally. The patient was referred to a dermatologist on May 17, who described red to blue confluent plaques arrayed in a linear, sporotrichoid fashion along the lateral forearm distal to the initial lesions at the far right in Fig. 1.
He obtained two 4 mm punch biopsies, one in formalin and one in broth for culture, and started Lamisil 250mg/d x 12d for this "painful, edematous cellulitis". Autolyzing neutrophils were the central element in this inflammation, surrounded by histiocytes and histiocyctic giant cells with an outer fringe of lymphocytres (Fig. 2). While this suppurative/granulomatous dermatitis was deemed most likely an infectious disease process, no fungal or mycobacterial agents could be found in initial PAS, GMS, Fite and acid-fast stains. New distal forearm lesions appeared while on Lamisil. On May 26, newer nodules from this "painful edematous cellulities" were biopsied, again with provision for microbiological culture. Cipro 500mg bid x 10d was prescribed. By June 8, the patient reported no improvement, in fact the older nodules were returning, so she was switched to Minocycline 100 mg/d x 7 d, without beneficial effect.
This progressive process is most likely: ______________________.
DIAGNOSIS: ATYPICAL MYCOBACTERIOSIS
This case illustrates: 1) Spiders are commonly unjustly accused; 2) Negative special stains for micro-organisms do not rule out infection; and 3) Biopsy of oddly configured inflammatory lesions should provide for microbiologic culture to include mycobacteria and fungi.
On June 13, WDS reported that microbiologic culture had produced a rapidly-growing acid-fast bacteria identified by DNA sequencing as Mycobacterium chelonei/abscessus complex, and to species by PCR as M. abscessus. (Several additional Fite-stained levels cut in retrospect finally showed rare organisms; see Fig. 3, oil mag.) A minimally effective trial of linezolid (Zyvox) was replaced by clarithromycin 500mg bid #30 that was continued for 72 days, alleviating pain. Thereafter, she was continued on topical DUAC gel with slow but steady improvement. By September 2006 the lesion was "all clear" and remained healed when last seen in June 2008. Unfortunately, there is then record of colon carcinoma metastatic to liver.
Nontuberculous mycobacteria (NTM) are acquired from the environment. M. abscessus is the most pathogenic and chemotherapy-resistant rapid-growing mycobacterium, commonly associated with contaminated traumatic skin wounds. It manifests as multiple lesions in 60% of cases and can be sporotrichoid, as in this immunocompetent woman.
Infections caused by NTM are usually associated with immunocompromised states. More recently, however, NTM infections are being diagnosed with greater frequency in patients lacking traditional risk factors. Municipal water treatment does not eliminate NTM. A pediatric epidemic in hands and feet was acquired in a public wading pool in Canada. A 34-year-old Korean female developed sporotrichoid M. abscessus infection on both forearms in a public bath where she worked. Investigation of a US 2000 outbreak among pedicure patrons noted an unusually large amount of debris behind foot spa recirculation screens that might have provided a niche for mycobacteria to colonize and proliferate to large numbers. Customers who shaved their legs before using the implicated foot spas were at higher risk for furunculosis than those who did not. In a series of acupuncture-associated mycobacteriosis, providing a known start point, the median incubation period was one month.
Absence of a pathognomonic clinical picture and variable histologic findings often delay diagnosis of NTM-induced cutaneous infections. Suppurative granulomas are the most characteristic feature in skin biopsy specimens from cutaneous NTM infections. Look for small clumps of bacilli at the center of clear spaces or vacuoles in the infiltrate. The Fite/Wade technic is superior to a regular Ziel-Nielsen ("acid fast") stain in demonstrating the more fragile NTMs because peanut oil used in the deparaffinization step protects the acid-fast elements in the capsule of the organisms. The auramine/rhodamine fluorescent stain remains the gold standard.
M. abscessus is resistant to most antimicrobial and tuberculostatic drugs. Clarithromycin or azithromycin are the only regular oral antimycobacterial agents with an effect, and should preferably be supplemented with other drugs such as Amikacin, since long-term monotherapy may cause resistance. Surgery can be curative, or at least helpful.
References: Upon request - rags@ccpathology.com
Acknowledgements: Thanks to clinicians Drs. Fred Novy and Garry Kolb for the detailed patient history.
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