Brown Recluse Spider

As spring approaches and people return to outdoor activities, caution should be taken in areas of the country that are home to Loxosceles reclusa, also called the brown recluse spider. A new study from St. Jude Children’s Research Hospital found that when patients present with sudden anemia, but the cause is elusive, the brown recluse spider should be part of the differential diagnosis, at least in parts of the nation where the spider is regularly found.


In a recent issue of The Journal of Pediatrics, St. Jude hematologists reported on six previously healthy adolescents hospitalized for treatment of acute, symptomatic anemia. The illnesses were linked to red blood cell destruction known as hemolytic anemia that was eventually traced to brown recluse spider bites. All six patients fully recovered, but four needed blood transfusions and three spent time in the intensive care unit.

Only three of the six patients recalled recent spider bites, and Jenny McDade, D.O., an assistant member in the St. Jude Hematology department, said the other wounds were only found after head-to-toe skin checks. McDade, the study’s lead author, said one bite was hidden by a bra strap and initially went unnoticed.

“The bite is often painless, and it is frequently missed,” she said, which is one reason St. Jude investigators decided to review hospital records to gauge the scope of the problem.

Although most people bitten by brown recluse spiders do not seek medical attention, the researchers noted that the spiders’ venom triggers a widespread reaction in about 30 percent of children. Although the exact mechanism is not completely understood, the most common systemic reaction is hemolytic anemia. Less commonly, kidney failure and clotting problems develop. Children seem to be more likely than adults to develop systemic complications, especially anemia. In rare cases, the researchers reported the bite has been linked to multi-organ failure and death.

Several times a year, St. Jude hematologists are consulted regarding patients who develop sudden, unexplained hemolytic anemia. This study focused on patients hospitalized for severe anemia who required hematology consultation during a one-year period at a general children’s hospital near the St. Jude campus in Memphis, Tenn.

Determining the cause of acute anemia is important to ensure the appropriate treatment, McDade said. For example, steroids may be used to treat some types of anemia, but are unproven when the cause is a brown recluse bite. “In the United States, the standard of care for treatment of brown recluse bites is supportive care and treatment of the wound,” she said.

McDade said most Americans should not worry about this spider, which carries a violin-shaped mark on its head and a preference for a quiet life lived in dry wood piles, under rocks or in corners of dark closets or attics. The spiders are found in parts of the Midwest and southern United States and are a regional problem. Although brown recluse bites are not a widespread cause of anemia, McDade said the diagnosis should be considered in patients with unexplained anemia who live in areas the spiders call home. Other St. Jude authors are Banu Aygun, M.D., and Russell Ware, M.D., Ph.D., St. Jude Hematology department chair and senior author.

Via Science Daily