OVERVIEW
Hyperlipoproteinemia type III is also known as wide beta disease and beta-lipoprotein dyslipidemia. It is a stand-alone disease with impaired catabolism of VLDLS, leading to accumulation of LDL precursors and intermediates. Electrophoresis of lipoproteins is suggestive of LDL mobility, while ultracentrifugation is suggestive of VLDLS. electrophoretic analysis shows wide beta-lipoprotein bands. There was considerable volatility in serum cholesterol (up to 1000 mg/ml) and triglycerides (up to 2000 mg/ml). Patients with hyperlipoproteinemia type III by isoelectric focusing electrophoresis show an apo-E2/E2 protein phenotype. apo-E mutant heterozygotes are a specific cause of hyperlipoproteinemia type III.
Etiology
Caused by higher than normal β-lipoproteins in serum. impaired catabolism of VLDLS leads to accumulation of LDL precursors and intermediates. Clearance defects are caused by mutant apo-E and are autosomal recessive. In addition to the apo-E2 homozygous purists, six other apo-E mutations have been found to cause the type III hyperlipoproteinemia phenotype in an autosomal dominant manner. However, manifestation of dyslipidemia on the basis of apo-E mutations seems to require the presence of secondary factors, such as metabolic factors causing impaired clearance of debris, which can be caused by lipoprotein excess. diabetes or alcohol consumption, or by factors that further impair lipoprotein clearance.
Symptoms.
Linear xanthomas and nodular xanthomas of the palms of the hands are characteristic manifestations of hyperlipoproteinemia type III, with nodular xanthomas, macular xanthomas, and tendon xanthomas occurring in 20% to 30% of cases of the disease. Coronary and/or peripheral vascular lesions occur frequently. Many patients also present with occult diabetes mellitus. Serum clouding, increased cholesterol and triglyceride levels Serum cholesterol and triglycerides have considerable fluctuation.
Examination
1. Lipid test items
Increased serum TC, serum HDL-C, serum TG serum LDL-C.
2. Review
If the first test reveals an abnormality, it is advisable to review the lipid level after 12 to 14 hours of fasting. serum cholesterol level may have a variation of 10% within 1 to 2 weeks, and the laboratory variation is allowed to be within 3%. at least 2 blood specimens should be examined before determining the presence of hyperlipidemia or deciding on preventive and curative measures.
Diagnosis
The diagnosis of type III hyperlipoproteinemia should be considered in patients with moderately to severely elevated plasma triglyceride and cholesterol concentrations. Typical cholesterol and triglyceride levels are 7.8 to 10.3 mmol/L (300 to 400 mg/dL) and 3.4 to 4.5 mmol/L (300 to 400 mg/dL), respectively. Because the disease is mostly invisibly inherited, there is frequently no family history of hyperlipidemia or early-onset CHD. Palmar or nodular xanthomas help make the diagnosis.
In the absence of palmar or nodular xanthomas, specific diagnosis will be more difficult and require special testing. If possible, measurement of VLDL cholesterol levels may reveal cholesterol-rich debris particles. Electrophoresis of lipoproteins is suggestive of LDL mobility, while ultracentrifugation is suggestive of VLDLS, electrophoretic analysis shows broad beta bands, and isoelectric focusing electrophoresis shows an apo-E2/E2 phenotype, or assessment of apo-E2 purity can be made by analyzing the apo-E genotype in DNA obtained from leukocytes.
Treatment
Because type III hyperlipoproteinemia is strongly influenced by coexisting metabolic factors, obesity, alcohol consumption, diabetes mellitus, and hypothyroidism must be aggressively sought out and treated. If these factors are identified and successfully treated, lipid abnormalities are usually corrected and plasma lipids return to normal without medication. In particular, type III hyperlipoproteinemia associated with hypothyroidism responds dramatically to thyroid hormone replacement therapy.
Dietary therapy should be geared toward limiting total fat, saturated fatty acids, and cholesterol and how feasible it is to restrict calories for weight loss. Treatment with estrogen should be considered in postmenopausal women, due to the fact that estrogen significantly reduces hyperlipidemia.
If dietary therapy and treatment of coexisting metabolic factors do not yield satisfactory results, pharmacologic therapy should be initiated with niacin, fibric acid derivatives, or HMG-CoA reductase inhibitors, all of which are effective in the treatment of the disease.
Prognosis
Varies according to the progression of coronary or peripheral vascular atherosclerosis.