Crohn’s disease (CD), a chronic inflammatory bowel disease, is characterized by transmural inflammation that can affect any part of the gastrointestinal tract. Histologically, the presence of non-caseating granulomas is considered a hallmark of CD, although they are not universally observed in all patients [1]. The exact pathogenesis of granuloma formation remains unclear, but it is believed to represent a dysregulated immune response to microbial antigens, with a central role played by macrophages, T-helper cells, and pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-α). Anti-TNF agents such as infliximab, adalimumab, and certolizumab have revolutionized the treatment landscape for moderate to severe CD [2]. By neutralizing TNF-α, these biologic therapies significantly reduce intestinal inflammation, induce mucosal healing, and improve quality of life. However, paradoxically, there have been emerging reports of granulomatous reactions in patients receiving anti-TNF therapy, raising questions about the immunological consequences of long-term TNF blockade [3]. These granulomatous lesions can mimic disease exacerbation or other pathologies like infections and sarcoidosis, complicating the clinical picture [4]. Crohn’s disease (CD) is a complex, immune-mediated inflammatory condition of the gastrointestinal tract that exhibits significant heterogeneity in both clinical presentation and histopathological findings [5]. One of the most distinctive histological features of CD is the presence of non-caseating granulomas, seen in approximately 15–36% of patients, depending on the site of biopsy and disease duration. Granulomas in CD are formed by aggregates of activated macrophages, often surrounded by lymphocytes, and are thought to represent a chronic immune response to persistent antigenic stimulation in genetically predisposed individuals [6]. Their presence is often used to differentiate CD from other inflammatory conditions, such as ulcerative colitis, and may be associated with more severe or complicated disease phenotypes [7].

The introduction of biologic agents, particularly tumor necrosis factor-alpha (TNF-α) inhibitors, has dramatically altered the management of CD. Anti-TNF agents such as infliximab, adalimumab, and certolizumab pegol have demonstrated robust efficacy in inducing and maintaining remission, reducing corticosteroid dependence, and promoting mucosal healing [8]. However, as with many biologics, their immunomodulatory effects can produce unintended consequences, including atypical immune reactions. Among these, the occurrence of new or persistent granulomas during anti-TNF therapy presents a paradox that challenges our current understanding of TNF-α's role in granulomatous inflammation [9]. Paradoxical granulomatous reactions, including sarcoid-like lesions, cutaneous granulomas, and granulomatous lymphadenitis, have been increasingly reported in patients treated with anti-TNF agents for various autoimmune diseases, not just CD. These observations suggest that while TNF-α is critical for granuloma formation, its inhibition does not universally prevent granulomatous inflammation and may, in some cases, trigger compensatory immune mechanisms [10]. This includes upregulation of other cytokines such as interferon-γ and interleukin-12, which can independently drive granuloma formation. Additionally, the shift from classical (M1) to alternative (M2) macrophage activation states in the absence of TNF-α may contribute to altered granuloma morphology or persistence. Clinically, these anti-TNF-associated granulomas pose significant diagnostic and therapeutic challenges [11]. In a CD patient presenting with new granulomatous inflammation during biologic therapy, distinguishing between disease relapse, paradoxical drug reaction, infectious etiology (such as tuberculosis), or even coexisting conditions like sarcoidosis becomes crucial. Misinterpretation can lead to inappropriate escalation of immunosuppression or delay in necessary antimicrobial treatment [12]. Moreover, the long-term implications of these granulomas on disease progression and treatment response remain poorly defined. Given these considerations, there is a pressing need for a systematic investigation into the clinical presentation, histological characteristics, and outcomes of CD patients who develop granulomas during anti-TNF therapy. Whether these granulomas signify therapeutic failure, immune adaptation, or a benign epiphenomenon is yet to be fully elucidated. Understanding the histopathological patterns and associated clinical parameters can help stratify patients more effectively and guide personalized treatment strategies [13].

Objective

This study seeks to fill this gap by conducting a detailed clinical and pathological evaluation of granulomatous lesions in CD patients undergoing anti-TNF treatment. It aims to compare the characteristics of these lesions with baseline disease histology, assess the potential triggers and patterns of occurrence, and determine their association with therapeutic outcomes.

This was a retrospective, observational, single-center study that included 75 patients diagnosed with Crohn’s disease and treated with anti-TNF agents, including infliximab or adalimumab, for at least 6 months were included. Patients were selected based on availability of both clinical follow-up data and histopathological specimens from intestinal biopsies or surgical resections performed during or after anti-TNF treatment.

Inclusion Criteria

• Confirmed diagnosis of Crohn’s disease based on clinical, endoscopic, and histological criteria
• Received anti-TNF therapy (infliximab or adalimumab) for ≥6 months
• Availability of biopsy or surgical specimen during anti-TNF therapy
• Age ≥18 years

Exclusion Criteria

• Patients with incomplete records or lost to follow-up
• Presence of concurrent infections such as tuberculosis, histoplasmosis, or fungal diseases
• Known sarcoidosis or other systemic granulomatous disorders before anti-TNF initiation
• Use of other biologics or immunomodulators without TNF inhibitor co-therapy

Data Collection

Clinical records were reviewed for demographic data, disease duration, phenotype (Montreal classification), anti-TNF agent used, duration of therapy, treatment response, and any paradoxical symptoms. Laboratory data, including CRP, ESR, fecal calprotectin, and imaging results, were collected when available. Histopathological slides were re-evaluated by two independent pathologists blinded to treatment outcomes. Granulomas were characterized based on morphology (e.g., necrotizing vs non-necrotizing), location (mucosal, submucosal, lymph node), cellular composition, and presence of associated inflammation, fibrosis, or ulceration. The primary outcome was the presence of granulomas during anti-TNF therapy. Secondary outcomes included:

• Clinical response to anti-TNF therapy (as defined by reduction in CDAI >70 points)
• Association of granulomas with treatment response or loss of response
• Morphological patterns of granulomas
• Need for escalation to alternative biologics or surgery

Statistical Analysis

Statistical analyses were performed using SPSS version 17.0. Descriptive statistics were used for demographic and clinical characteristics. Categorical variables were presented as frequencies and percentages, while continuous variables were expressed as means ± standard deviation. The chi-square test was applied for categorical comparisons. A p-value of <0.05 was considered statistically significant.

The study included 75 patients with Crohn’s disease receiving anti-TNF therapy. The mean age of participants was 42.8 ± 11.5 years, with a predominance of males (61.3%). The average duration of disease was 6.3 ± 3.7 years. Nearly a third of the patients (29.3%) had undergone previous surgical interventions for Crohn’s disease, while 24.0% reported a history of smoking.

Table 1: Demographics and Disease Characteristics of Study Participants (n = 75)

Among the 75 Crohn’s disease patients receiving anti-TNF therapy, granulomas were observed in 41.3% of cases (n = 31), while 58.7% showed no granulomatous inflammation. Of the granuloma-positive cases, 90.3% were non-caseating and 9.7% were caseating, indicating the predominantly non-necrotizing nature typical of Crohn’s pathology. Regarding distribution, most granulomas were located in the mucosal layer (67.7%), followed by the submucosa (22.6%) and mesenteric lymph nodes (9.7%), highlighting the variable histological involvement associated with granuloma formation in these patients.

Table 2: Granuloma Features and Distribution in Crohn’s Disease Patients (n = 75)

Among patients with granulomas, a significantly higher proportion experienced severe disease activity (58.1%) compared to those without granulomas (31.8%), with a p-value of 0.03. Mucosal healing at follow-up was more frequent in the granuloma-absent group (59.1%) than in those with granulomas (32.3%), reaching statistical significance (p = 0.02). Additionally, the need for surgery post-anti-TNF therapy was higher in patients with granulomas (29.0%) compared to those without (11.4%) (p = 0.04).

Table 3: Clinical Outcomes by Granuloma Presence

This study provides a detailed clinical and pathological evaluation of granuloma formation in patients with Crohn’s disease (CD) undergoing anti-TNF therapy, highlighting the relationship between granulomatous inflammation and clinical outcomes. Granulomas were observed in 41.3% of patients, with the majority being non-caseating in nature, consistent with the classical histological hallmark of Crohn’s disease. The presence of granulomas was significantly associated with higher disease activity and a greater need for surgical intervention, underscoring their potential role as markers of severe or refractory disease [14]. The findings align with earlier research indicating that granulomas may reflect a heightened immune response or persistent antigenic stimulation, particularly in patients who fail to achieve remission despite biologic therapy [15]. Interestingly, patients without granulomas demonstrated a higher rate of mucosal healing, suggesting that granulomatous inflammation may impair mucosal recovery or indicate a more chronic and fibrotic disease phenotype. This could be due to altered macrophage function or dysregulated cytokine signaling, especially involving interferon-gamma and tumor necrosis factor-alpha (TNF-α), both of which are pivotal in granuloma formation [16].

From a pathophysiological standpoint, anti-TNF therapy is known to modulate granuloma integrity. While effective in reducing systemic inflammation, it may also unmask or exacerbate localized granulomatous reactions due to paradoxical immune dysregulation [17]. This is particularly relevant in the subset of patients who develop paradoxical granulomatous lesions despite being on TNF inhibitors, suggesting a potential mechanistic divergence from classical TNF-mediated pathways. In our study, the few patients with caseating granulomas raised a differential diagnostic concern for co-existing infections like tuberculosis, which remains critical in endemic regions and should always be ruled out before initiating biologics [18]. Furthermore, the localization of granulomas predominantly in mucosal and submucosal layers indicates that endoscopic biopsy remains a valuable tool in histopathological surveillance. However, granulomas in lymph nodes or mesenteric fat, although less frequent, may carry prognostic value regarding disease spread or extra-intestinal involvement [19]. The study is limited by its observational design and moderate sample size, which may influence the generalizability of the findings. Additionally, the absence of longitudinal cytokine profiling or molecular markers restricts the mechanistic interpretation of granuloma dynamics. Nevertheless, the consistent associations between granuloma presence, severe disease, and poorer therapeutic response support the clinical relevance of these findings.

It is concluded that the presence of granulomas in patients with Crohn’s disease undergoing anti-TNF therapy is significantly associated with increased disease severity, higher rates of surgical intervention, and reduced mucosal healing. These granulomatous formations, predominantly non-caseating, may reflect a more aggressive or treatment-resistant disease phenotype.

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