prevalence of
hidradenitis suppurativa

Hidradenitis Suppurativa - the Orphan

The Rare Disease Act of 2002 (HR 4013) and the US Orphan Drug Act define a rare disease or condition as one that "(A) affects less than 200,000 persons in the United States, or (B) affects more than 200,000 in the United States and for which there is no reasonable expectation that the cost of developing and making available in the United States a drug for such disease or condition will be recovered from sales in the United States of such drug."  Statistically speaking, with a population of 282,100,000 (1), that's roughly .07% in the US.

Hidradenitis Suppurativa is classified as an Orphan Disease, and it must be for reasons of (B), because all estimates put us well above the .07% range...

Hidradenitis Suppurativa - the Numbers

Just how many people are we talking about?  Well, for the US alone, the estimates range between about 500,000 and 12 million! This is where this spread came from:

One of the earliest documented estimates comes from Gregor Jemec.  In the course of an androgen study conducted in 1988 in Copenhagen, Denmark, he found that "The prevalence of hidradenitis in the control group [of healthy women] was 4%." (2)  Today that would translate to 5.8 million women in the US.

Jan von der Werth mentions "Three studies have put the disease prevalence at between 1:100 and 1:600" (3) , meaning .2% to 1%. We have no references for these studies, but must assume they are of European origin. These estimates would translate to 564,200 to 2.8 million sufferers in the US.

In 1998, Jemec et al conducted a thorough prevalence study of hidradenitis in Denmark (4). The point-prevalence (one-time examination of 507 people) of HS was found to be 4.1%, and the one-year prevalence (based on subjective recollection of 599 people) to be 1.0%.  Extrapolating to today's US population, we'd find a point-prevalence of 11.6 million, and a period prevalence of 2.8 million.
Note: It is difficult to compare these numbers, since the period-prevalence is based on subjective evidence, whereas the point-prevalence was measured objectively. This may explain the low period number, which is typically higher than point.

Also in 1998, Brown & Rosen et al. stated "Hidradenitis suppurativa usually affects young women, with a prevalence of 0.3% to 4% in industrialized countries." (5)  We can't be sure if the numbers refer to women only, so it's either 432,000 to 5.8 million women or 846,300 to 11.3 million out of the total US population.

Again it is Gregor Jemec who finds a middle ground in 2004. "Hidradenitis suppurativa (HS) is a common skin disease affecting an estimated 2% of the population" (6), Although it sounds like a stab in the middle this time (he does not point to specific research), it translates to an agreeable 5.6 million people affected with HS in the US.

The first reference to an American estimate can be found in an article published on the eMedicine web site by Dr. Marina Jovanovic. She notes, "In the United States, the prevalence of HS appears to be 1-2% in the general population" (7), however, she does not give a reference for this number. Her international numbers seem to be based on Jemec's Danish prevalence study.  Given the above US percentages, we'd be in the 2.8 to 5.6 million range.

It is assumed that all figures above are point-prevalence numbers unless otherwise noted. Point-prevalence is a count taken at a point in time (as opposed to over a period of time). The number of affected people found is then compared to the total number of people examined/interviewed. The result is typically expressed as a percentage.

References:

(1) Women and Men in the US: March 2002
      US Census Bureau - March 2002 Current Population Survey (CPS)
 
     US Population: 282.1 million
     Women: 144 million (51%)
     Men: 138 million (49%)

(2) The symptomatology of hidradenitis suppurativa in women, JB Jemec
      Br J Dermatol. September, 1988

(3) Hidradenitis Suppurativa, Jan von der Werth
      Dermatology in Practice, Vol. 9 Num. 3

(4) Prevalence of hidradenitis suppurativa in Denmark,
      Jemec, Heidenheim, Nielsen
      Ugeskr Laeger., February 1998

(5) Hidradenitis Suppurativa, T. Brown, T. Rosen, I. Orengo
      December 1998, Southern Medical Journal

(6) Medical treatment of hidradenitis suppurativa
      Expert Opinion on Pharmacotherapy, 2004, vol. 5, no. 8

(7) Hidradenitis Suppurativa,  Marina Jovanovic, MD, PhD
      eMedicine, 8/18/2004