Malabsorption Syndromes

Malabsorption Overview - Leaky Gut Saga

• Definition: Impaired intestinal absorption of nutrients, leading to deficiencies & systemic effects.
• "Leaky Gut" Concept: Increased intestinal permeability due to compromised tight junctions (e.g., zonulin dysregulation). Allows passage of undigested food particles, toxins, & microbes, triggering inflammation.
• Mechanisms:
  • Pre-mucosal (Luminal): Defective hydrolysis (e.g., Pancreatic insufficiency, ↓bile salts).
  • Mucosal (Absorptive): Reduced surface area, enzyme defects, transport issues (e.g., Celiac disease, Crohn's disease).
  • Post-mucosal (Obstructive): Lymphatic blockage (e.g., Whipple's disease, intestinal lymphoma).

⭐ The D-xylose test helps differentiate between maldigestion (pancreatic) and malabsorption (small intestinal mucosal disease); it will be normal in pancreatic insufficiency.

Clinical Manifestations - Telltale Tummy Tales

• Growth: Failure to thrive (FTT), poor weight gain (<5th percentile), muscle wasting.
• GI Tract:
  • Chronic diarrhea (>2 wks): watery, fatty.
  • Steatorrhea: bulky, pale, foul, greasy stools.
  • Abdominal distension, pain, borborygmi.
  • Anorexia, vomiting.
• Nutrient Deficiency Clues:
  • Anemia (Iron, B12, Folate): pallor, glossitis.
  • Bleeding (Vit K): bruising, petechiae.
  • Bone (Vit D, Ca): rickets, tetany.
  • Eyes/Skin (Vit A, Zn): night blindness, xerophthalmia, dermatitis.
  • Protein: Edema.

⭐ Failure to thrive (FTT), chronic diarrhea, and abdominal distension form a classic triad for pediatric malabsorption.

Celiac Disease Deep Dive - The Gluten Grudge

• Pathophysiology: Immune response to gluten (gliadin) in HLA-DQ2/DQ8 individuals. Results in villous atrophy, crypt hyperplasia, ↑ Intraepithelial Lymphocytes (IELs).
• Clinical Features (Peds): Failure to thrive (FTT), chronic diarrhea, abdominal distension, Iron Deficiency Anemia (IDA), short stature. Dermatitis herpetiformis (DH).
• Diagnosis:
  • Serology:
    • Anti-tTG IgA (Best initial test). Check total IgA.
    • Anti-EMA IgA (Most specific).
    • Anti-DGP IgA/IgG (if IgA deficient or <2 yrs).
  • Duodenal Biopsy (Gold Standard): Marsh classification (e.g., Marsh III: villous atrophy).
  • Diagnostic Algorithm:

• Management: Lifelong strict Gluten-Free Diet (GFD). Nutritional support.
• Mnemonic (Symptoms - 📌 CELIAC):
  • Chronic diarrhea
  • Emesis
  • Lethargy
  • Irritability
  • Abdominal pain/distension
  • Constipation (sometimes)

⭐ *ESPGHAN: Symptomatic children with Anti-tTG IgA >10x ULN + positive EMA (2nd sample) may avoid biopsy for diagnosis of Celiac Disease.

Key Syndromes & Workup - Suspects & Sleuth Kits

• Key Syndromes & Primary Clues:

  Syndrome	Key Feature(s)	Primary Test(s)
  Cystic Fibrosis (CF)	Pancreatic insufficiency (steatorrhea), chronic lung disease	Sweat chloride (>60 mEq/L), ↓Fecal elastase, Genetic test
  Lactose Intolerance	Osmotic diarrhea, bloating post-dairy	Hydrogen breath test, Stool reducing substances (+), acidic pH
  Giardiasis	Foul steatorrhea, malabsorption; contaminated water	Stool microscopy (O&P - multiple), ELISA
  Short Bowel Syndrome	Post-surgical resection, nutrient deficiencies	Clinical Hx, Imaging, ↓D-xylose test

• General Workup (Sleuth Kit):

  • Stool: Microscopy (Giardia), Sudan stain (fat↑), fecal elastase, pH, reducing substances.
  • Blood: CBC (anemia), albumin, vitamins (A,D,E,K), PT/INR, IgA anti-tTG (Celiac screen).
  • Breath Tests: Hydrogen (lactose intolerance, SIBO).
  • D-xylose Test: Assesses proximal small bowel mucosal integrity.

    ⭐ D-xylose test: Normal in pancreatic exocrine insufficiency (e.g., CF) as absorption is independent of pancreatic enzymes, but abnormal in small intestinal mucosal disease (e.g., Celiac, SBS).

High‑Yield Points - ⚡ Biggest Takeaways

• Celiac Disease: Gluten-sensitive enteropathy, villous atrophy, anti-TTG/EMA antibodies.
• Cystic Fibrosis: Pancreatic insufficiency (steatorrhea), meconium ileus, elevated sweat chloride.
• Lactose Intolerance: Lactase deficiency, osmotic diarrhea, positive hydrogen breath test.
• Abetalipoproteinemia: AR, absent Apolipoprotein B, acanthocytes, severe fat malabsorption, neurological deficits.
• Shwachman-Diamond Syndrome: Pancreatic exocrine insufficiency, neutropenia, skeletal abnormalities.
• Giardiasis: Common parasite, foul-smelling watery diarrhea, diagnosis by stool antigen/microscopy.
• Short Bowel Syndrome: Post-surgical, reduced absorptive surface, requires TPN, risk of SIBO (Small Intestinal Bacterial Overgrowth).