Longstanding Perianal Ulcers

A 35-year-old Thai man presented with a perianal ulcerative lesion persisting for 10 years, refractory to antibiotics. He has experienced recurrent abscesses on the scalp, axillae, and perianal region since the age of 25, which progressed to multiple sinus tracts and extensive scarring in the perianal area—clinical features consistent with hidradenitis suppurativa (HS), Hurley stage III. However, he has not been adherent to treatment. He reported no history of fever, weight loss, chronic diarrhoea, abdominal pain, dysuria, or abnormal urine coloration. Examination revealed an erythematous plaque with an ulcer on a scarred HS background (Figure 1). No active HS lesions were present elsewhere. A pus swab for microbiological analysis (Figure 2) and a skin biopsy (Figure 3) from the perianal ulcer were performed. Pus from the perianal ulcer was acid-fast bacilli-positive. Skin biopsy revealed poorly defined granulomatous inflammation with histiocytes, lymphocytes, plasma cells, and multinucleated giant cells. Acid-fast bacilli were present, but mycobacterial polymerase chain reaction (PCR) and culture were negative. Human immunodeficiency virus and syphilis serology were negative. Chest radiography and sputum PCR were unremarkable. Following a 6-month course of standard antituberculosis therapy, the lesion resolved with scar formation and without any adverse drug reactions, such as cutaneous eruptions or hepatotoxicity. At the 2-year follow-up, there was no evidence of disease recurrence. Tuberculosis affects over 10 million individuals globally each year, with the highest incidence reported in Southeast Asia, China, India, and Africa [1]. Tuberculosis can manifest as skin lesions, classified into cutaneous tuberculosis (direct skin infection) and tuberculid (a skin reaction to tuberculosis). Cutaneous tuberculosis, a rare form constituting 1%–2% of extrapulmonary tuberculosis cases [1], has diverse clinical manifestations influenced by bacillary load, which reflects the host's cell-mediated immune response, and transmission route (either endogenous or exogenous). Periorificial tuberculosis arises from Mycobacterium tuberculosis spread from luminal structures to body orifices. Perianal tuberculosis may represent its manifestation in the perianal area resulting from gastrointestinal tract tuberculosis. In our case, colonoscopy was not performed to investigate further as the patient exhibited no gastrointestinal symptoms, despite the presence of chronic perianal ulcers, thereby reducing the likelihood of gastrointestinal tuberculosis. Pulmonary and perianal tuberculosis can coexist in approximately half of the patients [2]. Potential mechanisms include perianal contamination following the ingestion of sputum containing high bacilli or hematogenous spreading [2]. This rationale prompted the use of chest radiography and sputum testing in our case, both of which revealed no evidence of pulmonary tuberculosis. In the absence of evidence for pulmonary or gastrointestinal tuberculosis in our case, an alternative possibility is that the bacilli were acquired through an exogenous environmental route. Chronic inflammation from HS may induce local immunosuppression, increasing susceptibility to mycobacterial infection [3, 4]. Direct inoculation of environmental bacilli through perianal skin is also plausible, as pathogen remains viable in the environment for extended periods [5]. This presentation may be more consistent with primary inoculation tuberculosis, or tuberculous chancre, based on the ulcerative morphology, rather than tuberculosis verrucosa cutis, which typically manifests as a verrucous plaque. Although tuberculosis often affects immunocompromised individuals, only 18.6% of perianal tuberculosis cases occur in immunocompromised hosts [6]. Perianal tuberculosis can present as red-brown soft nodules, coalescing into large infiltrative plaques with ulcers, perianal abscesses, fistula-in-ano, anal fissures, or mass-like verrucous lesions, with the ulcerative form being most prevalent [2, 6]. Perianal tuberculosis can mimic conditions such as syphilis, fistulizing Crohn's disease, squamous cell carcinoma, extramammary Paget's disease, pyoderma gangrenosum, and HS. Due to its chronic, indolent course and varied clinical presentation, diagnosis is often delayed, as seen in our cases, with a mean symptom-to-diagnosis duration of 34.6 months [6]. HS is a chronic inflammatory skin condition affecting apocrine glands, prevalent in over 1% of the population in many European countries [7]. HS typically manifests in intertriginous and anogenital areas, characterised by inflammatory nodules, abscesses, sinus tracts, and scarring, where nodules and abscesses can rupture, forming ulcer in long-standing lesions. Misdiagnosis of perianal tuberculosis as HS has been documented due to shared morphological features [8]. Co-occurrence of both conditions has also been reported [9]. Several clinical clues suggest a lower likelihood of perianal HS in our case. First, HS is less common in Asian populations, whereas tuberculosis is more prevalent. Second, isolated perianal HS is rare without additional intertriginous involvement. Lastly, our case showed a chronic, progressive course rather than HS's typical recurrent pattern. Although HS is generally diagnosed clinically, in atypical perianal presentations, comprehensive investigations are recommended to rule out other conditions, particularly tuberculosis. The diagnosis of perianal tuberculosis primarily relies on identifying M. tuberculosis. In a study of 37 skin biopsy samples with different cutaneous tuberculosis types, positivity rates were highest with PCR (79.4%), followed by histopathology (73.5%), Löwenstein–Jensen media culture (29.4%), and smear examination (5.8%) [10]. Employing multiple diagnostic modalities improves sensitivity. Perianal tuberculosis is managed with standard tuberculosis therapy, typically leading to ulcer resolution within weeks. All authors contributed to the study's conception and design. Material preparation, data collection, and the drafting of the manuscript were performed by N.J., T.A., S.J. and V.P. critically reviewed the manuscript for important intellectual content. All authors have read and approved the final manuscript. We would like to thank Suteeraporn Chaowattanapanit MD and Nunsita Sittirach MD for providing the patient's information. Approval for this study was obtained from the Khon Kaen University Ethics Committee for Human Research (HE671625). The patient in this manuscript have given written informed consent for participation in the study and the use of his deidentified, anonymized, aggregated data and his case details (including photographs) for publication. Dr. Vincent Piguet has received grants from AbbVie, Bausch Health, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Eli Lilly, Incyte, Janssen, LEO Pharma, L'Oréal, Novartis, Organon, Pfizer, Sandoz and Sanofi; received payment or honoraria for speaking engagement from Sanofi; participated on an advisory board for LEO Pharma, Novartis, Sanofi, Union Therapeutics, Abbvie and UCB; and received equipment donation from L'Oréal. The remaining authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.