Chylomicron retention disease

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Chylomicron retention disease is an inherited disorder that impairs the normal absorption of fats, cholesterol, and certain vitamins from food. The features of chylomicron retention disease primarily affect the gastrointestinal system and nervous system.

Chylomicron retention disease begins in infancy or early childhood. Affected children have slow growth and weight gain, frequent (chronic) diarrhea, and foul-smelling stools (steatorrhea). They also have reduced blood cholesterol levels (hypocholesterolemia). Some individuals with chylomicron retention disease develop an abnormal buildup of fats in the liver called hepatic stenosis and can have an enlarged liver.

Other features of chylomicron retention disease develop later in childhood and often impair the function of the nervous system. Affected people may develop decreased reflexes (hyporeflexia) and a decreased ability to sense vibrations. Rarely, affected individuals have heart abnormalities or muscle wasting (amyotrophy).

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in a gene called SAR1B cause chylomicron retention disease. The SAR1B gene provides instructions for making a protein that is needed for the transport of molecules called chylomicrons. During digestion, chylomicrons are formed within cells called enterocytes that line the small intestine and absorb nutrients. Chylomicrons are needed to absorb fat-soluble vitamins and carry fats and cholesterol from the small intestine into the bloodstream.

SAR1B gene mutations cause the retention of chylomicrons within enterocytes and prevent their release into the bloodstream. Impaired chylomicron transport causes severely decreased absorption (malabsorption) of dietary fats and fat-soluble vitamins, leading to nutritional and developmental problems in people with chylomicron retention disease. Affected individuals are unable to absorb sufficient fats, cholesterol, and vitamins that are necessary for normal growth and development.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Chylomicron retention disease is a rare condition with approximately 50 cases described worldwide.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Diarrhea · Obligate (100%)

Abnormally increased frequency (usually defined as three or more) loose or watery bowel movements a day.

Elevated circulating hepatic transaminase concentration · Very frequent (99-80%)

Elevations of the levels of SGOT and SGPT in the serum. SGOT (serum glutamic oxaloacetic transaminase) and SGPT (serum glutamic pyruvic transaminase) are transaminases primarily found in the liver and heart and are released into the bloodstream as the result of liver or heart damage. SGOT and SGPT are used clinically mainly as markers of liver damage.

Fat malabsorption · Very frequent (99-80%)

Abnormality of the absorption of fat from the gastrointestinal tract.

Hypocholesterolemia · Obligate (100%)

An decreased concentration of cholesterol in the blood.

Retinopathy · Very frequent (99-80%)

Any noninflammatory disease of the retina. This nonspecific term is retained here because of its wide use in the literature, but if possible new annotations should indicate the precise type of retinal abnormality.

Steatorrhea · Very frequent (99-80%)

Greater than normal amounts of fat in the feces. This is a result of malabsorption of lipids in the small intestine and results in frothy foul-smelling fecal matter that floats.

Abdominal distention · Frequent (79-30%)

Distention of the abdomen.

Abnormality of vitamin metabolism · Frequent (79-30%)

An anomaly in the metabolism of a vitamin.

Failure to thrive · Frequent (79-30%)

Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.

Growth delay · Frequent (79-30%)

A deficiency or slowing down of growth pre- and postnatally.

Increased hepatocellular lipid droplets · Frequent (79-30%)

An abnormal increase in the amount of intracellular lipid droplets in hepatocytes.

Vomiting · Frequent (79-30%)

Forceful ejection of the contents of the stomach through the mouth by means of a series of involuntary spasmic contractions.

EMG: myopathic abnormalities · Occasional (29-5%)

The presence of abnormal electromyographic patterns indicative of myopathy, such as small-short polyphasic motor unit potentials.

Hepatic steatosis · Occasional (29-5%)

Steatosis is a term used to denote lipid accumulation within hepatocytes.

Other findings in the same source

From: Orphanet

Additional reported features include Visual impairment (Occasional (29-5%)); Acanthocytosis (Very rare (<4-1%)); Areflexia (Very rare (<4-1%)); Impaired proprioception (Very rare (<4-1%)); Myopathy (Very rare (<4-1%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Chylomicron retention disease is Metabolic Medicine, with a metabolic specialist / clinical geneticist as the relevant type of clinician. Paediatrician (children) or physician (adults), with metabolic specialist / clinical geneticist referral.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Is a biochemical or molecular result needed to clarify the diagnosis?
• Does this condition require an individual plan for illness or reduced food intake?
• Should nutrition advice come from a specialist metabolic dietitian?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Chylomicron retention disease. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.