Celiac Disease for the PA Exam

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Celiac Disease for the Physician Assistant Licensure Exam

Definition

Celiac Disease (CD): An autoimmune disorder in genetically predisposed individuals, triggered by ingestion of gluten (found in wheat, barley, and rye). It leads to inflammation and damage of the small intestine, particularly affecting the proximal small bowel (duodenum and jejunum), causing malabsorption.

Pathophysiology

Gluten Sensitivity: In celiac patients, gluten (specifically the gliadin component) is deamidated by tissue transglutaminase (tTG), which triggers an immune response in individuals with the HLA-DQ2 or HLA-DQ8 alleles.

Villous Atrophy: The chronic immune response damages the intestinal villi, leading to villous atrophy and subsequent malabsorption of nutrients.
Crypt Hyperplasia: Compensatory increase in crypt cells with a loss of functional surface area for nutrient absorption.
Intraepithelial Lymphocytosis: Increased T-lymphocytes in the intestinal epithelium due to inflammation.

Genetic Predisposition

Nearly all celiac patients carry the HLA-DQ2 or HLA-DQ8 gene. However, the presence of these genes alone is not sufficient for disease development, indicating environmental or additional genetic factors play a role.

Risk Factors

Genetic Predisposition: Family history of celiac disease significantly increases risk.
Other Autoimmune Disorders: There is a higher prevalence of celiac disease in patients with autoimmune conditions like type 1 diabetes, autoimmune thyroiditis, and Sjögren’s syndrome.

Clinical Features

Gastrointestinal (GI) Manifestations

Diarrhea: Chronic, foul-smelling, and greasy due to fat malabsorption (steatorrhea).
Weight Loss: Due to malabsorption, especially in untreated or advanced cases.
Abdominal Pain and Bloating: Commonly seen due to inflammation and fermentation of unabsorbed nutrients.
Iron Deficiency Anemia: Common due to impaired iron absorption in the duodenum.

Extraintestinal Manifestations

Dermatitis Herpetiformis: A pruritic, blistering skin rash typically found on the extensor surfaces, pathognomonic for celiac disease.
Neurological Symptoms: Peripheral neuropathy, ataxia, and headaches, possibly due to nutrient deficiencies or immune-related mechanisms.
Fatigue and Irritability: Common in untreated cases.

Diagnosis

Serologic Tests

IgA Anti-Tissue Transglutaminase (tTG) Antibodies: The most sensitive and specific initial test. However, in cases of IgA deficiency (more common in celiac disease), IgG tTG or IgG deamidated gliadin peptides (DGP) are used.
IgA Endomysial Antibodies (EMA): Highly specific but less commonly used due to cost.

Small Bowel Biopsy

Gold Standard: Endoscopic duodenal biopsy showing villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis confirms the diagnosis. Multiple biopsies are recommended due to patchy involvement.

Genetic Testing

HLA-DQ2/DQ8 Testing: Useful to rule out celiac disease if absent but not diagnostic, as these alleles are common in the general population.

Management

Gluten-Free Diet (GFD)

Lifelong Gluten-Free Diet: The cornerstone of treatment. Patients must avoid all gluten-containing foods (wheat, rye, barley). Even small amounts can trigger symptoms and intestinal damage.

Symptomatic improvement is typically seen within weeks, but intestinal healing may take months to years.

Nutritional Support

Vitamin and Mineral Supplementation: Iron, calcium, vitamin D, and folic acid supplementation may be necessary to correct deficiencies from malabsorption.
Dietary Counseling: Education about hidden gluten sources and cross-contamination risks is crucial to adherence.

Complications

Refractory Celiac Disease (RCD): Persistent symptoms and villous atrophy despite strict adherence to a gluten-free diet. It can progress to serious complications like enteropathy-associated T-cell lymphoma (EATL).
Malignancy: Long-standing untreated celiac disease increases the risk of gastrointestinal malignancies, particularly EATL and small bowel adenocarcinoma.
Osteoporosis: Malabsorption of calcium and vitamin D increases the risk of osteoporosis and fractures.

Key Points

Celiac disease is an autoimmune disorder triggered by gluten ingestion in genetically predisposed individuals, leading to small intestinal damage and malabsorption.
Diagnosis involves positive serologic testing (IgA tTG) and small bowel biopsy, showing villous atrophy and crypt hyperplasia.
The mainstay of treatment is a lifelong gluten-free diet, which improves symptoms and prevents complications.
Complications include refractory celiac disease, increased risk of intestinal malignancies (e.g., EATL), and osteoporosis due to chronic malabsorption.
Regular follow-up with serologic tests and nutritional monitoring is necessary to ensure compliance and detect complications.