Dysbetalipoproteinemia
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Usama Talib, BSc, MD [2]
Synonyms and keywords: Broad beta disease; broad beta hyperlipoproteinemia; broad-beta hyperlipoproteinemia; dysbetalipoproteinemia; familial dysbetalipoproteinemia; familial hypercholesterolemia with hyperlipemia; type III hyperlipoproteinemia
Overview
Familial dysbetalipoproteinemia is a autosomal recessive disorder passed down through families in which there are high amounts of cholesterol and triglycerides in the blood. This form is due to high chylomicrons and IDL (intermediate density lipoprotein). Also known as broad beta disease or dysbetalipoproteinemia, the most common cause for this form is the presence of ApoE E2/E2 genotype. It is due to cholesterol-rich VLDL (β-VLDL). Prevalence is 0.02% of the population.
Classification
Historical perspective
Pathophysiology
Pathophysiology
- Dysbetalipoproteinemia is a most commonly autosomal recessive disorder caused by mutations in Apo E gene:
- Apo E gene is located on the long arm of chromosome 19(19q13)
Pathogenesis
- Remnants of chylomicrons and VLDL are cleared from circulation by Apolipoprotein E.
- Apolipoprotein E serving as a ligand for the low-density lipoprotien receptor, mediates hepatic clearance of chylomicrons and VLDL remnants from circulation.
- Most common Apo E isoform is E 3/3, containing cysteine at position 112 and arginine at position 158.
- Homozygosity for the ApoE2 isoform , which has lower binding capacity to the LDL receptor, is present in majority of cases with Dysbetalipoproteinemia
- Besides Apo E2, naturally occurring Apo E mutations have also been describe to be associated with Dysbetalipoproteinemia. These are inherited in a dominant mode and expressed early in age.
- VLDL and chylomicron remnants that contains Apo E2 on their surface are not cleared as efficiently from the plasma. Resulting in formation of dense VLDL particle known as beta-VLDL.
- Accumulation of VLDL and chylomicrons results in atherosclerosis and dyslipidemia.
Causes
The cause of type 1 hyperlipidemia remains genetic.
Differential Diagnoses
Epidemiology and Demographics
Screening
There are no known screening recommendations for dysbetalipoprotenemia.
Natural History, Complication, Prognosis
Complications
Dysbetalipoprtenemia can cause the following complications [1]
- Atherosclerotic complications like coronary artery disease
- Pancreatitis
- Stroke
- Peripheral vascular disease
- Intermittent claudication
- Gangrene of the lower extremities
Prognosis
- Patients with dysbetalipoproteinemia have an increased risk for coronary artery disease and peripheral vascular disease.
- With treatment, most people show a significant reduction in lipid levels and thus the complications.
Diagnosis
Diagnosis of dysbetalipoprotenemia is confirmed[2] by the
- Presence of a palmar crease xanthoma, which is a rare diagnostic finding of dysbetalipoproteinemia.
- Lipid profile
- EKG is done to rule out cardiac involvement in patients with suspected laboratory findings
Molecular and Genetic testing
- Genotyping apoE. apo E-2 presence causes defective binding of apo E containing lipid particles.
- Ultracentrifugation or nuclear magnetic resonance lipid profiling
History and Symptoms
Symptoms of dysbetalipoprotenemia include [1] [3] [4]
- Xanthomas involving skin and tendons may be seen
- Chest pain can be the presenting compliant due to cardiac involvement
- Leg pain (due to peripheral arterial disease)
Physical Exam
Physical examination in dybetalipoproteinemia may range from being normal to the presence of these findings[1]
- Xanthoma Striatum Palmare-consisting of yellow streaks in the palmar creases.
- Tuberoeruptive xanthomas on the elbow or tibial tuberosities
- Cutaneous xanthomas
- Tendon xanthomas may also be seen rarely
Laboratory Findings
The laboratory findings consistent with dysbetalipoprotenemia include[5]the following
| Appearance | VLDL cholesterol | Cholesterol | Triglycerides | Isoelectric focusing |
|---|---|---|---|---|
| Floating
beta lipoproteins |
VLDL cholesterol
>0.35 |
Elevated | Elevated | ApoE-2 homozygote |
Treatment
Non-pharmacological therapy
- Dietary therapy with low cholesterol and fat diet has been shown to be effective.
- Inappropriate or subnormal control with non pharmacological therapies requires pharmacological treatment.
Medical Therapy
Dysbetalipoprotenemia can be treated[6] with the following options
- Bile acid binding agents are an option if TG levels are <200mg/dL
- Statins can be used if TG levels are <500mg/dL
- Fibrates and Nicotinic acid can otherwise be used.
Lipid lowering therapies can help decrease the symptoms e.g xanthomas and the complications associated with dysbetalipoprotenemia like the [7]
Genetic counselling
Genetic Counselling can be used to help the patients with dysbetalipoproteinemia and their families.
Prevention
- Screening the family members of those with familial dysbetalipoproteinemia may lead to early detection and treatment.
- Early treatment and avoiding other risk factors for vascular disease (such as smoking) are crucial to preventing early heart attacks, strokes, and blocked blood vessels.
References
- ↑ 1.0 1.1 1.2 Blom DJ, Byrnes P, Jones S, Marais AD (2002). "Dysbetalipoproteinaemia--clinical and pathophysiological features". S Afr Med J. 92 (11): 892–7. PMID 12506591.
- ↑ Rothschild M, Duhon G, Riaz R, Jetty V, Goldenberg N, Glueck CJ; et al. (2016). "Pathognomonic Palmar Crease Xanthomas of Apolipoprotein E2 Homozygosity-Familial Dysbetalipoproteinemia". JAMA Dermatol. doi:10.1001/jamadermatol.2016.2223. PMID 27603268.
- ↑ Cruz PD, East C, Bergstresser PR (1988). "Dermal, subcutaneous, and tendon xanthomas: diagnostic markers for specific lipoprotein disorders". J Am Acad Dermatol. 19 (1 Pt 1): 95–111. PMID 3042820.
- ↑ Eto M, Saito M (2013). "[Familial type III hyperlipoproteinemia]". Nihon Rinsho. 71 (9): 1590–4. PMID 24205719.
- ↑ Braunwald, Eugene. Heart Disease- Fourth Edition. Harvard Medical School: W. B. SAUNDERS COMPANY. p. 1137. ISBN 0-7216-3097-9.
- ↑ Hachem SB, Mooradian AD (2006). "Familial dyslipidaemias: an overview of genetics, pathophysiology and management". Drugs. 66 (15): 1949–69. PMID 17100406.
- ↑ Cho EJ, Min YJ, Oh MS, Kwon JE, Kim JE, Kim CJ (2011). "Disappearance of angina pectoris by lipid-lowering in type III hyperlipoproteinemia". Am J Cardiol. 107 (5): 793–6. doi:10.1016/j.amjcard.2010.10.063. PMID 21247547.