Clinical Pearls & Morning Reports
Published August 22, 2018
Eosinophils serve many functions in the body, including mediation of allergic responses, eradication of parasitic infections, and down-regulation of the inflammatory response. Read the latest NEJM Case Records of the Massachusetts General Hospital here.
Q: How is eosinophilia defined?
A: A normal absolute eosinophil count in the peripheral blood is 0 to 500 per cubic millimeter. Eosinophilia is defined as the presence of an absolute eosinophil count of more than 500 per cubic millimeter and is often categorized as mild (500 to <1500 eosinophils per cubic millimeter), moderate (1500 to 5000), or severe (>5000).
Q: Does the presence of a high viral load of human herpesvirus 6 (HHV-6) indicate active infection?
A: HHV-6 has the capacity to integrate into the human genome; this occurs in approximately 1% of the general population. After the virus integrates into the genome, very high viral loads (often >1 million copies per milliliter) can be detected in the blood but do not necessarily indicate active infection.
A: Symptoms of the DRESS syndrome often develop 2 to 8 weeks after the initiation of a new drug, and many drugs have been implicated in the DRESS syndrome, including proton-pump inhibitors and statins. The most frequently encountered culprit medications include antibiotics (e.g., sulfonamides) and anticonvulsant, antiviral, antipyretic, and analgesic agents. Once the diagnosis of the DRESS syndrome is established, prompt identification and discontinuation of the causative drug are mandatory. In most cases, clinical judgment is sufficient to determine the most likely causative drug. For more challenging cases, in which the patient has been exposed to multiple new drugs, clinical tests have been developed to aid in identification of the causative agent. These include patch tests and lymphocyte transformation tests.
A: After the suspected causative drug is withdrawn, supportive therapy is provided to patients with the DRESS syndrome. If erythroderma is present or the body surface is extensively affected by exfoliative dermatitis, then treatment in a specialized intensive care unit or burn unit may be required. If considerable visceral organ injury or organ failure is identified, then immediate organ-specific medical therapy is provided and the appropriate specialists are involved. Despite prompt discontinuation of the causative drug, symptoms of the DRESS syndrome typically last for more than 15 days and may persist for several months. Guidelines for the treatment of the DRESS syndrome are limited, and evidence for systemic treatment is derived from case series and expert opinion. Systemic glucocorticoids are considered to be first-line therapy. A dose of prednisone of 1.0 mg per kilogram of body weight per day or the equivalent, with gradual tapering over a period of 3 to 6 months, is often recommended. In milder cases of the DRESS syndrome, high-potency topical glucocorticoids may be sufficient for relief of symptoms. Glucocorticoid-sparing agents have been used in a small number of cases of the DRESS syndrome, with varying efficacy. The DRESS syndrome is associated with reactivation of human herpesviruses, especially HHV-6, in the majority of cases. The use of antiviral drugs that are effective against HHV-6 has been proposed for the treatment of patients who have the DRESS syndrome and confirmed HHV-6 reactivation; however, evidence is insufficient to support the use of such treatment.