USMLE/COMLEX 2 - Malabsorption Syndromes

Here are key facts for USMLE Step 2 & COMLEX-USA Level 2 from the Malabsorption Syndromes tutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links.

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1. Malabsorption presents with diarrhea, steatorrhea, weight loss, weakness, anemia, and vitamin and mineral deficiencies. 2. Diagnosis involves patient history (stool type & frequencies, weight loss), blood tests for specific nutrient deficiencies, fecal fat tests, and Sudan III staining. 3. Further investigation may require endoscopy, colonoscopy with biopsy, breath tests, or small bowel x-rays. 4. Malnutrition can lead to musculoskeletal, neurologic, and cardiac complications (night blindness in Vitamin A deficiency, peripheral neuropathy from deficiencies in Vitamins B1, B6, B12, edema in protein deficiency). 1. Occurs when >90% of pancreatic enzyme function is lost, causing malabsorption of fats and fat-soluble vitamins (A, D, E, K, and B12). 2. Top causes: Pancreatitis (often from alcohol in adults), cystic fibrosis (most common in children), and obstructive tumors. 3. Clinical presentation: Loose, bulky, oily, pale feces that float due to oil content; pain starting in left epigastric area radiating to the back (in pancreatitis). 4. Diagnosis: Reduced duodenal pH and fecal elastase-1 (FE-1), an enzyme marker of pancreatic secretion. 1. Caused by deficient lactase activity, with worldwide prevalence >65%, varying by population (~30% Europe, ~50% US, ~70% Asia, nearly 100% Africa). 2. Three types: Congenital (rare autosomal recessive), primary (adult-type, common), and secondary (transient due to intestinal damage). 3. Pathophysiology: Undigested lactose pulls water into intestines causing osmotic diarrhea; bacterial fermentation produces short-chain fatty acids and gas causing pain, bloating, flatulence. 4. Diagnosis: Hydrogen breath test (>20 ppm increase after lactose solution indicates deficiency), blood glucose tests, DNA tests, stool acidity tests. 1. Autoimmune-mediated inflammatory disorder triggered by gliadin (gluten protein) found in wheat, barley, and rye, affecting 1% of US adults. 2. Screening: Serological markers including IgA anti-tissue transglutaminase (tTG-IgA, tTG-IgG), deamidated gliadin peptide antibodies, and anti-endomysial antibodies (EMA-IgA). 3. Definitive diagnosis requires endoscopy with small bowel biopsy showing characteristic changes with gluten exposure and improvement with gluten removal. 4. Genetic markers include HLA-DQ2 and HLA-DQ8 haplotypes (useful for ruling out celiac disease). 1. Rare disorder occurring in tropical regions (parts of India, Pakistan, Puerto Rico, Haiti, Cuba) with uncertain etiology (likely infectious or environmental). 2. Characterized by malabsorption of folic acid and Vitamin B12, leading to megaloblastic anemia. 3. Diagnosis requires biopsy showing villous atrophy, increased crypt depth, epithelial cell enlargement, increased lymphocytic and inflammatory cells. 4. Must be differentiated from celiac disease through serologic testing. 1. Rare infection caused by Tropheryma whipplei (gram-positive, PAS-positive bacilli), most common in older European-descent males with immune defects. 2. Clinical presentation: Begins with arthralgias, can include neurologic symptoms (dementia), endocarditis, and later GI effects (diarrhea, abdominal pain, weight loss). 3. Diagnosis: PAS-positive staining after small bowel biopsy showing foamy macrophages in lamina propria and villous atrophy. 4. PCR testing for T. whipplei DNA in CSF is crucial due to potential neurologic complications.

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1. Exocrine Pancreatic Insufficiency: Treated with lifestyle modifications (alcohol cessation), vitamin supplements, and exogenous pancreatic enzyme administration. 2. Lactose Intolerance: Managed by reducing consumption of lactose-rich foods; patients need to determine their personal tolerance threshold. 3. Celiac Disease: Strict gluten-free diet is the only effective treatment. 4. Tropical Sprue: Treated with folic acid and Vitamin B12 supplementation plus antibiotics (tetracycline, ampicillin). 5. Whipple Disease: Treated with antibiotics (ceftriaxone or penicillin, followed by trimethoprim/sulfamethoxazole); fatal if untreated, and relapses are common. 1. EPI causes primarily fat malabsorption because carbohydrate and protein digestion can be maintained by amylase and protease from other organs (salivary glands, stomach, small intestine). 2. Primary vs. secondary lactase deficiency: Intestinal villi appear normal in primary lactose intolerance but damaged in secondary cases. 3. Lactose intolerance differs from milk allergy, which is an immune-mediated reaction to cow's milk proteins. 4. Celiac disease histopathology shows increased lymphocytes, mucosal inflammation, villous atrophy, and crypt hyperplasia upon gluten exposure, which improve with gluten removal. 5. On endoscopy, celiac disease shows "scalloping" of duodenal folds and increased vascularity (reflects villous atrophy and edema). 1. Celiac disease is associated with dermatitis herpetiformis (approximately 10% of patients), reduced bone density due to calcium deficiency, and increased malignancy risk. 2. Secondary lactase deficiency is caused by intestinal damage from infections, food allergies, and other conditions. 3. Whipple disease can cause disabling neurologic effects if untreated. 4. Tropical sprue and celiac disease have similar histopathology, requiring serologic tests for differentiation. 5. EPI from chronic pancreatitis can result in loss of both endocrine and exocrine functions, leading to diabetes mellitus.

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Below is information not explicitly contained within the tutorial but important for USMLE & COMLEX 2. 1. Monitoring response to therapy: Assessment tools and laboratory markers to evaluate treatment effectiveness. 2. Refractory celiac disease: Approach to patients who don't respond to gluten-free diet. 3. Nutritional rehabilitation strategies: Staged approach to malnourished patients with malabsorption. 4. Management of complications: Approach to osteopenia, anemia, and other sequelae of chronic malabsorption. 5. Surgical options: When to consider surgical intervention in malabsorptive disorders. 1. Pregnancy considerations: Management of malabsorption disorders during gestation. 2. Pediatric approach: Age-specific presentations and management differences. 3. Elderly patients: Atypical presentations and comorbidity considerations. 4. Post-bariatric surgery malabsorption: Recognition and management of iatrogenic malabsorption. 5. Immunocompromised patients: Modified diagnostic approach and treatment considerations. 1. Novel diagnostic tools: Advances in capsule endoscopy, molecular testing, and biomarkers. 2. Role of microbiome: Influence on malabsorption and potential therapeutic targets. 3. Non-celiac gluten sensitivity: Differentiation from celiac disease and management approach. 4. Pharmacologic advances: New enzyme supplements and targeted therapies. 5. Quality of life assessment: Tools to evaluate functional status and treatment success beyond laboratory parameters.