Chylomicron retention disease is a disorder of fat absorption. It is associated with SAR1B. Mutations in SAR1B prevent the release of chylomicrons in the circulation which leads to nutritional and developmental problems. It is a rare autosomal recessive disorder with around 40 cases reported worldwide. Since the disease allele is recessive, parents usually do not show symptoms.Without functional chylomicrons, certain fat-soluble vitamins such as vitamin D and vitamin E cannot be absorbed. Chylomicrons have a crucial role in fat absorption and transport, thus a deficiency in chylomicron functioning reduces available levels of dietary fats and fat-soluble vitamins. History
Chylomicron Retention Disease, also called Andersons disease, is an autosomal recessive lipid malabsorption syndrome characterized by abnormally low amounts of cholesterol in the blood. This disease most frequently is diagnosed in infants. Charlotte Anderson first published a description of the disorder in 1961, where she observed a seven month old girl who developed intestinal mucosa filled with fat droplets. In 2003, Jones and colleagues identified mutations in the SAR1B gene, which transcripts the SAR1B protein involved in COPII transport and proposed this was the molecular defect of the disorder. To present day, 17 mutations of the SAR1B gene have been discovered. This disease is rare, with only 50 cases diagnosed worldwide. Genetics
The Sar1B GTPase is an enzyme located in epithelial cells of the gastrointestinal tract. These proteins are critical for release of chylomicrons in the body.Chylomicron retention disease is an autosomal homozygous recessive disorder arising from mutations in the gene encoding the Sar1B GTPase.
Before the PCTV leaves the ER, it is incorporated into a COPII coatomer of five proteins. The PCTV undergoes a similar mechanism for budding as normal COPII transport vesicles. Though PCTV does not require COPII coatomer proteins for budding from the ER, association with the coatomer is necessary for docking and fusion with the cis-golgi network. In chylomicron retention disease, the PCTV vesicles are competent for budding from the ER membrane but are defective for fusion with the cis-golgi body. Sar1B is a GTPase and one of the five proteins of the COPll coatomer. A mutation in the sar1B gene and subsequently the sar1B protein are the common genetic origins of chylomicron retention disorder. Without the fully functional sar1B protein, the COPll coatomer proteins engulf pre-chylomicrons exiting the ER but are unable to disassemble upon arrival at the cis-Golgi, preventing membrane fusion with this organelle. Signs and symptoms
Physical symptoms of CMRD involving development and function of the gastrointestinal tract and nervous system typically manifest  between  infancy and adolescence. The symptoms of CmRD are similar to the physical symptoms  of malnutrition, as the disease arises due to the poor absorption of lipids and fat-soluble nutrients such as vitamin E. For this reason, the disease is likely to be under-diagnosed by physicians . Fat-soluble nutrients are essential for growth, development, and normal bodily function. Vitamin E deficiency is especially serious, as the vitamin is necessary for proper neurological function and development. Without Vitamin E, neurons cannot operate correctly and signals from the brain are weakened.