Pathology of graft vs host disease and histopath lesion Robbins based md pathology exam answer
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Graft-versus-host disease (GVHD): pathology and histologic lesions
Definition: GVHD is an immunologically mediated complication of allogeneic hematopoietic stem-cell transplantation in which immunocompetent donor T lymphocytes recognize recipient tissues as foreign and damage them.
It may also occur after transfusion of non-irradiated cellular blood products in immunodeficient recipients.
Conditions required for GVHD
- The graft contains immunocompetent T cells.
- The recipient expresses antigens, usually HLA antigens, not present in the donor.
- The recipient cannot effectively reject the donor lymphocytes.
Pathogenesis
GVHD is a donor T-cell-mediated type IV hypersensitivity reaction.
- Tissue injury from conditioning (radiation/chemotherapy) activates host antigen-presenting cells and releases inflammatory cytokines, especially TNF and IL-1.
- Host APCs present recipient alloantigens to donor CD4+ and CD8+ T cells.
- Donor T cells proliferate and release cytokines such as IFN-gamma, TNF, and IL-2.
- Cytotoxic donor T cells and inflammatory cytokines induce epithelial-cell apoptosis and tissue destruction.
The principal target organs are:
- Skin
- Gastrointestinal tract
- Liver
A key microscopic hallmark is epithelial apoptosis.
Acute GVHD
Classically occurs within the first 100 days after transplantation, although clinicopathologic features, not time alone, define acute GVHD.
Gross/clinical lesions
- Skin: erythematous maculopapular rash that may progress to generalized erythroderma, bullae, and epidermal detachment resembling toxic epidermal necrolysis.
- GIT: anorexia, nausea, vomiting, profuse watery diarrhea, abdominal pain, ileus, and bleeding in severe cases.
- Liver: jaundice and cholestatic liver dysfunction.
Histopathology of acute GVHD
| Organ | Characteristic histopathologic lesion |
|---|---|
| Skin | Vacuolar interface dermatitis with basal-cell degeneration; individual apoptotic/dyskeratotic keratinocytes; satellite-cell necrosis, where lymphocytes closely appose dying keratinocytes; sparse lymphocytic infiltrate. Severe disease shows subepidermal clefting, epidermal necrosis, and denudation. |
| GIT | Crypt epithelial apoptosis is the earliest and most characteristic lesion. There is cryptitis, crypt-cell dropout, dilated damaged crypts, crypt abscesses, mucosal ulceration, and finally complete mucosal denudation. In the small bowel, Paneth-cell loss may occur. |
| Liver | Portal tract lymphocytic infiltrate with damage to small intrahepatic bile ducts. Bile-duct epithelial apoptosis, vacuolization, and duct injury cause cholestasis. Severe disease may show bile-duct loss and canalicular cholestasis. Hepatocyte apoptosis may also be present. |
Important lesion to write in exam
Apoptosis of epithelial cells in skin, intestinal crypts, and bile ducts is the characteristic histologic feature of acute GVHD.
Current pathology literature likewise identifies epithelial apoptosis as the core lesion, especially in intestinal biopsies, while emphasizing clinical correlation because drugs and infections can mimic it (GI GVHD pathology study).
Chronic GVHD
Chronic GVHD has autoimmune-like and fibrosing features. It may involve skin, oral cavity, eyes, liver, lungs, fascia, joints, and genital tract.
Histopathology
1. Skin
Two major patterns:
- Lichenoid pattern: resembles lichen planus, with interface dermatitis, basal-cell vacuolization, apoptotic keratinocytes, and band-like lymphocytic infiltrate.
- Sclerodermatous pattern: dermal fibrosis with thickened collagen bundles, loss of adnexal structures, subcutaneous septal fibrosis, and fascial involvement in severe disease.
2. Oral mucosa
- Lichenoid interface mucositis
- Basal-cell degeneration
- Apoptotic keratinocytes
- Subepithelial fibrosis
- Salivary gland involvement may cause lymphocytic sialadenitis, acinar destruction, and xerostomia.
3. Liver
- Chronic cholestatic injury
- Injury and progressive loss of small bile ducts
- Portal fibrosis and, rarely, biliary cirrhosis
4. Lungs
- Bronchiolitis obliterans is characteristic.
- There is concentric fibrosis and narrowing or complete obliteration of small airways.
5. GI tract
Chronic mucosal injury may produce architectural distortion, crypt loss, mucosal atrophy, and fibrosis. Histology alone often cannot reliably distinguish late acute GVHD from chronic GVHD (NIH pathology consensus review).
Acute versus chronic GVHD: short comparison
| Feature | Acute GVHD | Chronic GVHD |
|---|---|---|
| Dominant mechanism | Donor T-cell cytotoxicity and cytokine injury | Immune dysregulation with fibrosis and autoimmune-like injury |
| Main organs | Skin, gut, liver | Skin, oral cavity, eyes, liver, lungs, fascia, genital tract |
| Main microscopic lesion | Epithelial apoptosis | Lichenoid interface injury and fibrosis |
| Skin pattern | Interface dermatitis, keratinocyte apoptosis | Lichenoid or sclerodermatous changes |
| Gut lesion | Crypt apoptosis and crypt dropout | Atrophy, architectural distortion, fibrosis |
| Lung lesion | Less typical | Bronchiolitis obliterans |
Conclusion for exam
GVHD results from donor T-cell attack on recipient tissues after allogeneic transplantation. Acute GVHD primarily damages skin, intestinal crypt epithelium, and intrahepatic bile ducts, with epithelial apoptosis as the hallmark. Chronic GVHD resembles autoimmune disease and is characterized by lichenoid inflammation and progressive fibrosis, including scleroderma-like skin disease and bronchiolitis obliterans.
One-line viva answer:
The characteristic histologic lesion of acute GVHD is apoptosis of target epithelial cells, especially basal keratinocytes in skin, crypt cells in intestine, and bile-duct epithelium in liver.
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