Updates-By Carol A. Kemper, MD, FACP
TB Lymphadenitis: Where’s the AFB?
Source: Prasoon D. Acta Cytol 2000; 44:297-300.
Prasoon examined the cytological yield of fine-needle aspirates for acid-fast bacilli (AFB) by Zeihl-Neelsen stain in 783 lymph node aspirates, 213 (27.2%) of which were positive for tuberculosis (TB) based on microbiologic, clinical, and therapeutic outcome. AFB were visualized in 87 of 213 (40.8%) specimens. There was a significant difference in the likelihood of detecting AFB depending on whether the aspirate appeared to be mixed blood-particles (31% of cases), caseous (45%), or purulent (23%). Purulent aspirates, with lots of neutrophils and necrosis, were most likely to have positive smears (72%). While these aspirates could be cytologically confused with that of a supporative bacterial lymphadenitis, these lymph node abscesses were clinically "cold"—a clue to the presence of TB. Aspirates that appeared caseous with a modest granulomatous response were smear-positive 62.5% of the time. On the other hand, only 3% of aspirates with mixed blood-particles with a predominant granulomatous response and no evidence of necrosis were AFB-smear positive.
Prasoon argues that a vigorous Th-1 mediated immune response with enhanced activation of macrophages and intracellular killing would result in a better granulomatous response with little tissue destruction. A less vigorous response would result in poor granuloma formation, more tissue destruction and eventual liquefaction of the node, with larger numbers of AFB. In other words, the presence of a vigorous granulomatous response in needle aspirates (or biopsy specimens) of suspicious lymph nodes is inversely related to the presence of visible AFB. Smear-negative lymph nodes with well-formed granulomata should always be suspected of TB—and TB smears should always be requested on purulent specimens from cold abscesses.
Construction Kicking up Cocci in Tucson
Sources: Leake JA, et al. J Infect Dis 2000;181:1435-1440; ProMED-mail post 5/3/00; www.promedmail.org.
Housing construction in the burgeoning counties of Pima, Maricopa, and Pinal outside of Tucson, Ariz., is kicking up dust—so much so that cases of coccidioidomycosis have jumped 50% in some areas. Public health officials reported in the Arizona Daily Star that cases of coccidioidomycosis have risen 30% statewide during the past year, in large part due to the rapid expansion of Tuscon into the surrounding desert. Authorities point out that the two greatest risk factors for cocci in this area are housing construction combined with an elderly population. Many people moving into this area have never been exposed to the soil fungus and are non-immune. Pinal County is reporting the highest rate of the three counties, at 53.8 cases per 100,000 (a total of 396 cases in 1999), although these figures may be underreported by at least half. Figures in the elderly are higher at 80 cases per 100,000.
While this may seem like a problem limited to Arizona physicians, think again about your own practice. Many elderly patients migrate to Arizona for the winter months, or like my parents from Minnesota, spent several weeks there last winter visiting friends lucky enough to have moved there a couple of years ago. Travel to these areas is a risk factor for cocci, although the infection may land on your doorstep weeks to months after the patient returns from their trip. A former fellow in our lab, Richard Tucker, MD, who now practices Infectious Diseases in Wenatchee, Wash., estimates that approximately 2% of his Arizona travelers convert their skin tests every year. Elderly persons who have recently moved to Arizona, especially those who have smoked, taken steroids, or who have congestive heart failure, cancer, or HIV, are at greatest risk for symptomatic disease.
Ouch! Penile Tuberculosis from BCG
Source: Latini JM, et al. J Urol 2000; 163:1870.
An unfortunate elderly man with transitional cell carcinoma of the bladder developed progressive dorsal penile nodules and a coronal abscess two weeks after completion of a six-week course of weekly intravesicular bacillus Calmette-Guerin (BCG) (a live attenuated strain of Mycobacterium bovis). The BCG treatment had been uneventful except for transient dysuria following the final installation. The coronal abscess failed to respond to incision and drainage, and antibiotics. Excisional biopsy was performed, which showed non-caseating granulomata and fibrous tissue. Cultures for HSV, bacteria, and fungi were negative and AFB smears were negative. Eventually, M. bovis grew from culture, and the lesions quickly responded to antituberculous therapy. Interestingly, the man had contracted pulmonary tuberculosis in 1955 in Korea requiring segmental lobe resection and nine months of treatment with isoniazid and p-aminosalicylic acid.
Urethral and penile complications from intravesicular BCG are rare but should be suspected in patients with evidence of penile induration or infection in whom routine cultures are negative, irrespective of the results of AFB smears. Current recommendations support the use of PCR in such cases, which may have resulted in a speedier diagnosis.