microvillus inclusion disease

Microvillus inclusion disease is a very rare malabsorption syndrome that primarily presents in the neonatal period with severe, persistent secretory diarrhea. The condition is linked to pathogenic variants in the MYO5B gene, which disrupts the normal function of intestinal cells. Infants are typically affected from birth, and the disease has been described as being so uncommon that it affects fewer than 1 in 1,000,000 people. The clinical presentation and underlying genetic cause are critical for confirming the diagnosis and guiding management.

A defining feature of microvillus inclusion disease is protracted or intractable diarrhea that begins in the neonatal period. This chronic secretory diarrhea is the primary and nearly universal clinical finding, leading to significant challenges with nutrition and growth from the start of life. Although diarrhea is the most prominent symptom, individual experiences may vary and not all aspects of the condition are present in every case. Not all individuals experience all features, and severity varies considerably.

Microvillus inclusion disease is caused by pathogenic variants in the MYO5B gene. The MYO5B protein plays an important role in the proper trafficking and organization of cellular components in intestinal cells, and mutations disrupt the formation of microvilli, leading to defective nutrient absorption and fluid regulation. The condition is inherited in an autosomal recessive pattern, meaning that an affected individual inherits two copies of the mutated gene, one from each parent. It is more common when parents share a common ancestor, which increases the likelihood that both carry the rare variant. Genetic counseling is recommended for families to understand the implications for family planning.

Currently, management of microvillus inclusion disease focuses on supportive care and symptom management, as no treatments have been approved specifically for this condition. This approach typically involves careful fluid and electrolyte management, nutritional support, and other individualized strategies implemented by a multidisciplinary team. Since there are no foundational or FDA-approved treatments available, care is tailored to the needs of each patient. Genetic counseling is recommended to help families understand treatment options and plan for the future.

Outcomes for microvillus inclusion disease vary considerably depending on the severity of symptoms, the timing of diagnosis, and the level of specialized care available. The condition is lifelong and poses significant challenges, particularly due to persistent issues with nutrient absorption, yet improvements in supportive care have helped many individuals manage complications over time. Outcomes described in medical literature continue to evolve as standards of care improve. Families often find it helpful to connect with genetic counselors to understand inheritance implications and access additional support resources.

Clinical trials are underway exploring new treatment approaches for microvillus inclusion disease. Individuals interested in clinical trials can search ClinicalTrials.gov or consult their care team about eligibility.