JPGN Reports · 6 authors, 4 centres
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This study compares isolated perianal Crohn's disease (CD) and hidradenitis suppurativa (HS) in a small series of 7 patients. Key distinguishing features include the presence of fistulae and perianal location on MRI for CD, versus gluteal abscesses and bilaterality for HS. Biopsy showing granulomas and ASCA positivity support CD, while a multidisciplinary approach is essential for accurate diagnosis and treatment.
**Background:** Hidradenitis suppurativa (HS) is a rare skin disease with recurrent nodules, abscesses, and fistulae in apocrine gland-bearing areas, with a prevalence of 1%–4% and a female-to-male ratio of 3:1. Crohn's disease (CD) is a chronic inflammatory bowel disease that can present with perineal fistulas, fissures, abscesses, and skin tags. Isolated perineal CD is unusual and can be difficult to distinguish from HS, posing a diagnostic challenge for gastroenterologists. This study aimed to determine criteria that distinguish perineal CD from perineal HS.
**Methods:** This retrospective study included all patients with isolated perineal CD (per European Society of Pediatric Gastroenterology and Nutrition criteria) or perineal HS followed at a tertiary center. Data on gender, age at onset, weight, body mass index, anti-Saccharomyces cerevisiae antibodies (ASCA), MRI, biopsies, extraperineal locations, CD Paris classification, and HS Hurley classification were collected. Patients with luminal CD were excluded.
**Key Results:** Four patients with isolated perineal CD (3 girls, 1 boy; ages 9–16) and 3 with perineal HS (all boys; ages 9–15) were included. Among CD patients, all had fistulae, 2 had granulomas on skin biopsies, 2 had granulomas on rectal biopsies, and 3 of 4 were ASCA positive. MRI showed sinus tracts in 4/4 CD patients, all extrasphincteric and perianal, with lymphadenopathy in 3/4 and rectal wall thickening in 1/4. In HS patients, all had abscesses (3/3), bilateral in all cases, superficial, and located in the gluteal region (3/3) or sacral/gluteal (3/3); only 1/3 had a sinus tract. No HS patient had perianal lesions, lymphadenopathy, or rectal wall thickening. Treatment for CD included infliximab (all 4) and azathioprine (3/4). HS patients received antibiotics (all 3), with 1 improving on infliximab, 1 on adalimumab, and 1 worsening on both biologics requiring IV antibiotics and surgery.
**Clinical Implications:** Isolated perineal CD is rare (0.82% of CD patients in this center). Distinguishing features include fistulae on MRI (especially extrasphincteric and perianal), granulomas on biopsy, ASCA positivity, and perianal location. HS is characterized by gluteal abscesses, bilaterality, superficial lesions, and absence of perianal involvement or rectal wall thickening. A multidisciplinary approach involving gastroenterologists, dermatologists, and radiologists is crucial for accurate diagnosis and optimal treatment.