New‐Onset Perianal Eroded Lesion in a Pediatric Patient

An 11-year-old previously healthy girl presented with a painful, eroded plaque in the perianal area for 8 days. The lesion was initially painless and later became tender to wiping. She denied recent trauma, pruritus, or drainage. She tried topical mupirocin without improvement. Her medical history was unremarkable, with up-to-date immunizations, no known allergies, and no history of gastrointestinal symptoms such as abdominal pain, constipation, or bloody stools. She had recently traveled to Japan, where she had a brief, self-resolved fever. Family history included pemphigus vulgaris in her father and paternal grandmother, and constipation on her maternal side. Physical examination revealed an 8-mm eroded, non-fluctuant, ovoid papule in the perianal region without drainage (Figures 1 and 2). A 3 mm punch biopsy was performed (Figure 3). Histopathology revealed full-thickness ulceration with underlying granulomatous inflammation (H&E; ×100) (Figure 3). Special stains, including Gram, GMS, PAS, Giemsa, AFB, and Fite, were negative for infectious organisms. Immunostains for CMV, EBV, HSV, and spirochetes were also negative. Mycobacterial and fungal PCR testing were negative. Immunohistochemistry highlighted CD163-positive histiocytes, CD3-positive T-cells, focal CD20-positive B-cells, and rare CD30-positive enlarged lymphoid cells. SOX-10 and pan-keratin immunostains were negative for melanocytic or epithelial neoplasms. Laboratory tests showed mild thrombocytosis (432 × 103/μL; reference range 143–398 × 103/μL) and an elevated ESR (37 mm/h; reference range 0–10 mm/h) while the comprehensive metabolic panel was unremarkable. Given the biopsy findings of full-thickness ulceration and granulomatous inflammation, cutaneous Crohn's disease was favored, and the patient was referred for gastroenterology evaluation. Stool calprotectin was elevated (311 μg/g; reference range < 50 μg/g), indicating intestinal inflammation. Magnetic resonance enterography revealed mild terminal ileum thickening and enlarged mesenteric lymph nodes. Histopathologic evaluation of colonoscopic biopsies confirmed patchy granulomatous inflammation with Paneth cell metaplasia and focal architectural distortion, consistent with early Crohn's disease. A representative high-powered photomicrograph highlights a non-caseating granuloma, circled in red, within the colonic mucosa (H&E stain; original magnification ×200) (Figure 4). The patient was initiated on IV infliximab infusions (10 mg/kg) at weeks 0, 2, and 6 for induction, followed by maintenance dosing every 5 weeks. She demonstrated significant improvement in both cutaneous and gastrointestinal symptoms after 4 months of treatment. Cutaneous Crohn's disease (CCD) is a significant extraintestinal manifestation of Crohn's disease, occurring in approximately 40% of patients [1]. Although CCD can affect various sites, perianal involvement represents a particularly challenging and diagnostically complex presentation, especially in pediatric patients. This case of an 11-year-old girl presenting with an atypical perianal lesion, later diagnosed as CCD, highlights the importance of maintaining a high index of suspicion for inflammatory bowel disease in children presenting with persistent, unusual perianal skin findings, even in the absence of gastrointestinal symptoms. In pediatric patients, cutaneous manifestations can precede intestinal involvement in Crohn's disease in about 6%–36% of patients [2]. Perianal CCD can mimic a range of infectious and autoimmune dermatologic conditions, making diagnosis particularly challenging. Viral etiologies such as HSV and CMV typically present as grouped vesicles or solitary punched-out ulcers, respectively [3]. However, negative immunostains rendered these diagnoses less likely. Bacterial causes include Staphylococcus aureus, which may present with eroded papules or honey-colored crusted plaques and surrounding cellulitis. Streptococcus pyogenes infection presents as sharply demarcated bright red patches [4]. Ecthyma gangrenosum classically evolves from painless red patches to hemorrhagic pustules, gangrenous tissue, and necrotic ulcers [5]. In our patient, the absence of signs of systemic infection, immunocompromised history, and negative staining made an infectious etiology less likely. Inflammatory conditions such as pyoderma gangrenosum typically present with a rapidly progressive, painful ulceration; however, it lacks granulomatous inflammation on histology [6]. Hidradenitis suppurativa often manifests with multiple nodules or abscesses in intertriginous areas but similarly lacks granulomatous inflammation on histology [7]. Behçet disease may uncommonly involve perianal ulcerations but is typically accompanied by systemic manifestations of oral and genital aphthosis, vasculitis, and uveitis, features not present in this patient [8]. Eroded perianal discoid lupus erythematosus (DLE), although uncommon, presents as erythematous, scaly, coin-shaped plaques, and in this case, lacked the histopathologic findings of interface dermatitis with basal layer vacuolization or follicular plugging [9]. In our patient, the presence of surface ulcerations with lymphohistiocytic inflammation within the dermis on skin biopsy, in addition to non-caseating granulomas observed on the histopathology of the colonic tissue, confirmed the diagnosis of CCD and excluded more common infectious and inflammatory etiologies [1, 2]. The treatment of CCD in pediatric patients requires special consideration due to potential impacts on growth and development. Although topical and systemic corticosteroids, antibiotics, and immunosuppressants have shown mixed results, biologic therapies have demonstrated promise in managing both cutaneous and intestinal manifestations of Crohn's disease [10]. The treatment choice should be tailored to the individual patient, considering disease severity, extent of involvement, and potential side effects. In conclusion, this case underscores the need for clinicians to maintain a high index of suspicion for atypical perianal lesions as potential early signs of Crohn's disease. Early recognition, biopsy, and appropriate multidisciplinary management are essential to optimize outcomes and minimize long-term complications in these young patients. The authors declare no conflicts of interest.