Hidradenitis suppurativa: number of diagnosed patients, demographic characteristics, and treatment patterns in the United States.

Recent regional and insurance database studies indicate that diagnoses of hidradenitis suppurativa (HS) are rare, with fewer than 200,000 affected patients in the United States. These findings are at odds with the generally accepted prevalence of approximately 1%. To estimate the number of patients diagnosed with HS, including patients enrolled in public health plans and the uninsured, we performed an investigation using National Center for Health Statistics databases of visits to health care providers. Survey data from physician offices and clinics, hospital outpatient departments, and emergency departments in the United States were analyzed. There were 254,000 (95% confidence interval: 180,000, 328,000) health care visits by patients with HS per year from 2002 to 2010. An annualized estimate of 118,000 (95% confidence interval: 83,000, 152,000) patients with HS diagnoses was determined. Excluding emergency department data, the annualized estimate was 100,000 (95% confidence interval: 67,000, 134,000) patients. Adults between 18 and 64 years of age comprised 92.8% (standard error, 2.6%) of HS patients. Of that working-age population, 31.5% (standard error, 5.6%) were enrolled in Medicare or Medicaid, which is a significantly higher proportion than for those in the same age group in the general population. A review of earlier surveys of HS prevalence was performed. HS is a rarely diagnosed disease, and epidemiologic data to support undiagnosed HS as a common disease are lacking.