What Is Abetalipoproteinemia?

Familial abnormal beta lipoproteinemia (FD) is also known as type III hyperlipoproteinemia. After the patient's plasma lipoprotein was separated by ultracentrifugation, and agarose electrophoresis was performed, it was found that the very low-density lipoprotein (VLDL) electrophoresis often moved to the position instead of the normal pre- position. -VLDL. Structural analysis of these -VLDLs found that their cholesterol content was very rich. Because -VLDL is the most prominent manifestation of type III hyperlipoproteinemia and has obvious family aggregation, it is called familial abnormal -lipoproteinemia.

Basic Information

nickname: Type III hyperlipoproteinemia
English name: familial dysbetalipoproteinemia
English alias: familial type 3 hyperlipopro-teinemia

Visiting department: Endocrinology
Common causes: Apo E caused by abnormal mutations, genetic or environmental factors
Common symptoms: Xanthomas of the skin

Causes of familial abnormal beta lipoproteinemia

It is currently believed that type III hyperlipoproteinemia is caused by multifactorial abnormalities. In addition to the abnormal variation of Apo E, it is often necessary to incorporate other genetic or environmental factors. The abnormality of Apo E causes a metabolic disorder of lipoproteins (CM, VLDL, and IDL) containing Apo E, while other genetic or environmental factors may cause increased triglyceride-rich lipoprotein synthesis. When both are present, significant hyperlipoproteinemia is produced.

Clinical manifestations of familial abnormal -lipoproteinemia

Age of onset

The disease is rare in childhood and adolescence, and only a few cases have been reported so far. Male patients are more common than females, and the age of onset of male patients is significantly earlier than females. Women usually develop the disease after menopause. At the same time diabetes or hypothyroidism can also make the age of the disease earlier.

Yellow tumor

Patients often have multiple skin xanthomas. Because some xanthomas do not appear in other types of hyperlipoproteinemia, they have certain clinical diagnostic significance. The most characteristic of these is palm stripe-shaped yellow tumors, that is, yellow lipid deposits appear at the folds of the palm surface. About half of the untreated patients see this xanthomas. In addition, other types of xanthomas can be seen, such as nodular or nodular xanthomas. Nodular xanthomas are often found at the elbows, knees, and knuckles, but they are not unique. Macular and tendon xanthomas are sometimes seen, but tendon xanthomas are more common in familial hypercholesterolemia.

3. Early-onset atherosclerosis

Early-onset or accelerated atherosclerosis is seen in 1/3 to 1/2 of patients. Atherosclerotic lesions occur in the blood vessels around the lower limbs as often as in the coronary arteries. It may be related to the significant increase of its plasma -VLDL concentration.

About one third of patients have coronary heart disease. The age of symptom onset of vascular involvement in male patients (mean 40 years) was earlier than that of female patients (mean 50 years). If plasma cholesterol levels rise significantly, the risk of atherosclerosis is high.

4. Concomitant diseases

Certain systemic diseases are often present and may exacerbate the disease. Nearly 1/2 of the patients had elevated plasma uric acid levels, but most patients were asymptomatic, and only 4% of patients developed clinical gout. However, few people develop diabetes. Hypothyroidism, if coexisted with this disease, will aggravate its dyslipidemia. In contrast, hyperthyroidism can reduce dyslipidemia and even make hyperlipidemia disappear.

Familial abnormal beta lipoproteinemia

1. The ratio of VLDL-cholesterol / plasma triacylglycerol 0.3 (mg / mg) is of diagnostic significance for this disease; and a ratio 0.28 (mg / mg) suggests that this may be the disease.

2. VLDL-cholesterol / VLDL-triacylglycerol ratio This ratio is 1.0 (mmol / mmol) is very valuable for diagnosis.

3. Plasma cholesterol and triacylglycerol concentrations are significantly increased. Plasma cholesterol concentration is usually higher than 7.77mmol / L (300mg / dl) and can be as high as 26.0mmol / L. The increase in plasma triacylglycerol concentration (if measured in mg / dl) is roughly equal to or higher than the plasma cholesterol level.

4. Plasma LDL is reduced, HDL is normal or slightly reduced.

5. VLDL showing mobility in plasma electrophoresis.

Diagnosis of familial abnormal beta lipoproteinemia

The most reliable biochemical marker for the diagnosis of this disease is the determination of the Apo E phenotype or Apo E genotype.

Treatment of familial abnormal beta lipoproteinemia

For most patients, blood lipid levels can often be reduced to normal through dietary treatment or simultaneous correction of coexisting metabolic disorders. The so-called coexisting metabolic disorders refer to hypothyroidism, obesity, uncontrolled diabetes, and excessive drinking. Generally speaking, the first treatment of hyperlipidemia is to consider diet therapy. The basic method is to limit the intake of calories to overweight people and reduce the content of saturated fatty acids and cholesterol in food.

If 6-month diet does not reduce blood lipid levels to normal, medication should be initiated. The available therapeutic drugs include niacin, trihydroxytrimethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (Statin), cellulose aromatic acids, and fish oil.

Prognosis of familial abnormal beta lipoproteinemia

The clinical manifestations of arteriosclerosis in men with this disease appear around 50 years old, and peripheral vascular disease is common. The incidence of coronary heart disease is also increasing; peripheral vascular disease and coronary heart disease are more common in women in the postmenopausal period than in patients without this disease.