Summary
Chylomicron retention disease (CMRD) or Anderson disease is an exceptional and particular form of hypobetalipoproteinemia (see this term) characterized by the absence of intestinal apolipoprotein B-48 (ApoB-48) and reduced levels of LDL cholesterol. It is very rare, only about 20 cases have been reported in the world to date. Chylomicron retention disease manifests in infancy or early childhood. It is often associated with growth delay, hepatomegaly with steatosis, diarrhea with steatorrhea and fat malabsorption. Except in the case of Marinesco-Sjogren syndrome (MSS; see this term), there are no neurological or neuromuscular effects. The disease is transmitted in an autosomal recessive manner and is a result of mutations of the SAR1B gene (SARA2; 5q31.1) coding for a protein (COPII) implicated in the assembly and secretion of chylomicrons by the intestine. The disease is suspected after lipid analysis, carried out on the patient and their parents after 12 hours of fasting, showing seriously decreasing levels of LDL (<0.80g/L) and ApoB (<0.50g/L) while the level of triglycerides can be normal, or even moderately augmented (<3g/L), associated with a normal or low level of HDL (<0.40g/L) and a decreasing level of ApoA1 (<0.60g/L). Diagnosis is based on the absence of ApoB-48 in serum after taking lipids orally, and the appearance of `white intestine' seen endoscopically. The evidence of mutations on two alleles of the SAR1B gene confirms the diagnosis. Differential diagnoses include all pathologies associated with fat malabsorption and steatosis, as well as central and/or atypical peripheral neuropathies. Genetic counseling should be offered to affected families and lipid and hepatic analysis after 12 hours of fasting should be carried out on their relatives. Prenatal diagnosis is possible when the causal mutations in both parents are known. Management is done in highly specialized gastroenterologic units. Life expectancy is reduced as a result of growth delay caused by malabsorption. *Author: Dr P. Benlian (May 2009)*.
