The Role of Microvilli in Intestinal Function
Microvilli are microscopic cellular membrane protrusions that increase the surface area for absorption and secretion in various organs, most importantly in the small intestine. They are covered with a layer known as the
glycocalyx, which contains enzymes crucial for the final stages of digestion. The integrity of microvilli is essential for efficient nutrient absorption.
Histological Features of Microvillous Atrophy
On a
histological examination, microvillous atrophy is identified by a near-complete absence or severe reduction of microvilli on the apical surface of
enterocytes. This is often accompanied by an abnormal
brush border and the presence of vesicle-like structures within the enterocytes, indicating an intracellular trafficking defect.
Genetic Basis and Pathophysiology
Microvillous atrophy is often associated with mutations in the
MYO5B gene, which encodes a myosin motor protein critical for the transport of vesicles containing microvillus membrane proteins. Mutations disrupt normal trafficking, leading to defective microvilli formation and function. The condition is inherited in an
autosomal recessive pattern.
Clinical Manifestations
Infants with microvillous atrophy present with intractable diarrhea, severe dehydration, and failure to thrive. The malabsorption leads to nutrient deficiencies, which can manifest as a range of clinical symptoms including
hypoproteinemia and electrolyte imbalances. These symptoms require immediate medical attention and often lifelong nutritional support.
Diagnosis
The diagnosis of microvillous atrophy is based on clinical presentation, histological findings, and genetic testing. Histological examination of a
small bowel biopsy typically reveals the characteristic absence of microvilli. Genetic testing can confirm mutations in the MYO5B gene or other related genes.
Treatment and Management
There is no cure for microvillous atrophy, and management focuses on supportive care. This includes
total parenteral nutrition (TPN) to bypass the defective intestinal absorption, and electrolyte management to prevent dehydration. In some cases,
intestinal transplantation may be considered as a treatment option.
Prognosis
The prognosis for individuals with microvillous atrophy varies. Early diagnosis and appropriate management can improve outcomes, but the condition remains life-threatening. Long-term prognosis depends on the severity of the disease and the effectiveness of the supportive care provided. Research and Future Directions
Current research is focusing on understanding the molecular mechanisms underlying microvillous atrophy and developing potential gene therapies. Advances in
stem cell research and regenerative medicine offer hope for future treatments that could restore normal intestinal function in affected individuals.
