SCOTTSDALE – Stevens-Johnson syndrome and toxic epidermal necrolysis are not quite as rare as previously thought, according to one of the first population-based epidemiologic studies of the disorders.
“The incidence of Stevens-Johnson syndrome appears to be higher than previously reported, though mortality rates are lower,” said Derek Hsu of Northwestern University in Chicago, together with his associates. Both diagnoses were linked to a number of immune system disorders, “suggesting that immune dysregulation contributes to these diseases,” the investigators added.
Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are potentially life-threatening mucocutaneous conditions that are usually triggered by medications or infections. In 1991, a population-based study in three U.S. states reported annual incidence rates of 7.1, 2.6, and 6.8 cases per million individuals for SJS, SJS/TEN, and TEN, respectively.
More recent studies have been limited mostly to case series, and the current incidence, mortality, and health care costs of those conditions among adults in the United States were unknown, Mr. Hsu and his coinvestigators noted.
Therefore, they analyzed data for 2009 through 2012 from the Nationwide Inpatient Sample, which covers 20% of hospitalizations in the country. Using validated ICD-9 codes, the researchers extracted information on patients with Stevens-Johnson syndrome and/or toxic epidermal necrolysis. To improve the positive predictive value of the diagnostic codes, they excluded patients with concurrent diagnoses of bullous dermatoses or erythema multiforme major.
The estimated annual incidence of SJS ranged from 8.6 to 9.8 cases per million adults per year, with a mean of 9.3 cases per million population, Mr. Hsu and his coinvestigators reported at the annual meeting of the Society for Investigative Dermatology.
Rates of combined SJS/TEN and TEN were substantially lower, with means of 1.6 and 1.9 cases per million per year, respectively.
Inpatients who were black, Hispanic, Asian, Native American, or of mixed race or ethnicity were more likely to have those diagnoses than were white inpatients, as were Medicare and self-pay patients and patients with relatively more comorbidities.
Patients diagnosed with SJS stayed in the hospital an average of 9.8 days, incurring $21,407 in mean inflation-adjusted treatment costs, while patients with SJS/TEN or TEN stayed an average of more than 16 days, with associated costs of nearly $59,00 and $53,700, respectively. For all three diagnostic categories, length of stay and costs were significantly greater than among inpatients as a whole, Mr. Hsu and his associates noted.
Age- and sex-adjusted case-fatality rates were lower than previously reported, ranging from 3.7% to 7.5% for SJS (average, 4.7%), from 15.7% to 22.3% for SJS/TEN, and from 7.7% to 19% (average, 14.8%) for TEN. The risk of mortality increased very little after the affected body surface exceeded 10%, the researchers noted. Septicemia, other infections, renal failure, cancers, and older age all increased the risk of mortality.
After accounting for race, age, and sex, SJS/TEN were significantly associated with a number of comorbidities, including systemic lupus erythematosus, renal failure, liver disease, epilepsy, and HIV disease, as well as mycoplasma, tuberculosis, and other serious infections, the researchers also found.
In addition, SJS and TEN were significantly more likely among inpatients with non-Hodgkin lymphoma, multiple myeloma, and leukemia. “Further studies are needed to understand the mechanism of these associations,” the investigators said.
The Dermatology Foundation and the Agency for Healthcare Research and Quality funded the study. Mr. Hsu had no disclosures.