Atypicals on the rise? Data seem to say yes
Atypicals on the rise? Data seem to say yes
Hot tubs and showers could be the causes
On the stage of TB control, the atypical mycobacterial infection traditionally plays a bit part — It’s an annoying minor character who shows up mostly to confuse people trying to interpret tuberculin skin test reactions.
But what if the incidence of atypicals suddenly began to increase? It’s a perturbing question that constantly intrigues Gwen Huitt, MD, an infectious disease specialist who studies atypicals at National Jewish Hospital in Denver.
"Those of us who spend our lives studying atypicals feel that, in the past 10 years, there’s clearly been an exponential rise in the percent of cases we’re seeing," she says. The question is whether that rise represents a true increase or just a better ability on the part of laboratories to identify the bugs, she adds.
If the increase represents a true increase in the number of cases, what’s causing it? "Are we taking more showers and aerosolizing these bacteria? Are we building into environments we shouldn’t be living in, such as swamps? We don’t have the answer yet," she continues. "But most of us who do this feel it’s an emerging crisis because we don’t yet have a cure for some of these things."
If infection with atypicals was reportable, as is TB disease, it would be easier to understand what’s going on, Huitt says. "I’ve talked to people at [the Centers for Disease and Control and Prevention] and asked why we can’t make these things reportable for a year or two so we can see what kind of data we get," she says. "So far, they haven’t been interested."
Data suggest that, along with the M. avium complex, there is an apparent increase in cases of infection with rapid-growing mycobacteria, which include M. chellonae and M. abscessus, both in the Southeastern and Gulf states. Huitt says the data also suggest there may be an increase in M. simiae, which is found mostly in Arizona, Texas, and eastern Washington state. The rapid growers are no picnic, she says. As for the desert-dwelling M. simiae, it’s "a terrible infection, a highly resistant organism for which we have no cure at present."
The Lady Windemere syndrome’
TB experts have long known that atypicals can cross-react with TB skin test antigens. But it’s still not known whether all atypicals produce a reaction to tuberculin, Huitt adds. The well-known studies of Navy recruits done three decades ago suggest that atypicals are concentrated in the Southeastern states. Skin-test readers are supposed to take that into account when they’re working among populations in, say, Georgia, as opposed to Colorado, she says.
Along with geographic indicators, atypical infections seem to go with a certain physical type, Huitt says. Researchers have described one phenotype, the so-called Lady Windemere syndrome. "That’s a woman who is tall and thin, and who may have a touch of scoliosis. She may also have a touch of pectus excavatum or pectus caranatum — abnormalities of the breastbone, such that it either caves in, curves out." Such women tend to get M. avium infections that settle in the middle areas of their lungs, for reasons that aren’t yet understood, Huitt says.
Subscribe Now for Access
You have reached your article limit for the month. We hope you found our articles both enjoyable and insightful. For information on new subscriptions, product trials, alternative billing arrangements or group and site discounts please call 800-688-2421. We look forward to having you as a long-term member of the Relias Media community.