Microvillus Inclusion Disease

Microvillus Inclusion Disease (MVID) is a **rare, congenital intestinal disorder** that primarily affects infants and newborns. It is caused by genetic mutations that disrupt the normal function of the epithelial cells lining the small intestine, leading to **life-threatening diarrhea** and severe malabsorption.

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### **Key Features of MVID**

#### 1. **What Happens in MVID?**

• **Microvilli**, which are tiny finger-like projections on the surface of intestinal cells (enterocytes), are either absent or abnormally trapped inside the cells in vesicles called "microvillus inclusions."
• Microvilli are essential for nutrient absorption, and their dysfunction leads to severe diarrhea and inability to absorb nutrients.

#### 2. **Genetic Cause**

• MVID is caused by mutations in genes involved in intracellular trafficking:
• **MYO5B**: Most common mutation.
• **STX3** and **STXBP2**: Less common mutations.
• It is inherited in an **autosomal recessive** manner, meaning both parents must pass on a defective gene for the child to develop the disease.

#### 3. **Clinical Symptoms**

• Symptoms usually appear within the **first days or weeks of life**.
• **Severe diarrhea**: Watery and persistent.
• **Dehydration**: Due to fluid loss.
• **Failure to thrive**: Poor growth and malnutrition.
• **Electrolyte imbalance**: Low levels of essential minerals due to diarrhea.
• **Complications**:
• Dependence on **parenteral nutrition** (IV feeding).
• Risk of infections, liver damage, and sepsis from long-term IV feeding.

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### **Diagnosis**

• **Histopathology and Electron Microscopy**:
• Flattened villi in the intestine (villus atrophy).
• Microvillus inclusions visible inside enterocytes.
• **Genetic Testing**: Identifies mutations in MYO5B, STX3, or STXBP2 genes.
• **Immunohistochemistry**: May show abnormal protein expression in epithelial cells.

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### **Treatment**

• **No Cure**: MVID cannot be cured, but symptoms can be managed.
• **Supportive Care**:
• **Total Parenteral Nutrition (TPN)**: Provides nutrients intravenously to ensure growth and survival.
• Infection control: Prevent complications like sepsis.
• **Intestinal Transplantation**:
• In severe cases, intestinal or combined liver–intestine transplantation may be considered for long-term survival.

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### **Prognosis**

• Without transplantation, prognosis is poor due to complications from TPN (e.g., infections, liver damage).
• Advances in transplant surgery and supportive care have improved survival rates.

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### **In Simple Terms**

Microvillus Inclusion Disease is a genetic disorder where babies are unable to absorb nutrients because their intestinal cells lack functioning microvilli. This leads to severe diarrhea, malnutrition, and dependence on IV feeding to survive. Treatment focuses on managing symptoms, and intestinal transplantation may offer a chance for better long-term outcomes.

Would you like additional information on **genetic inheritance patterns**, **recent research**, or **support groups** for families dealing with MVID?