Hyperlipoproteinemia type 5
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ;Associate Editor(s)-in-Chief: Shivani Chaparala M.B.B.S [2]
Synonyms and keywords: : Hyperchylomicronemia,Late-Onset, Hyperchylomicronemia With Hyperprebetalipoproteinemia, Familial, Mixed Hyperlipidemia, Type V Hyperlipemia, Hyperlipidemia Type V, Type 5 Hyperlipoproteinemia, Type 5 Hyperlipemia, Type 5 HPL, Type V HPL, Combined Fat And Carbohydrate Induced Hyperlipidemia, Mixed Hypertriglyceridemia.
Overview
Hyperlipoproteinemia type 5 is a severe type of autosomal dominant inherited hyperlipidemia, characterised by inability to break down triglycerides and cholesterol which results in increase levels of chylomicrons and VLDL. It is a more complicated form of type I and more closely related with acquired environmental factors but no association with reduced Lipoprotein lipase or apolipoprotein C-II activity as in type I.
Pathophysiology
The absence of manifestations until middle age, suggest that the cause of type V hyperlipoproteinemia(HPL) is multifactorial including a combination of environmental, hormonal and genetic factors. Type V may be found in families with other forms of hyperlipoproteinemias such as type III and type IV. VLDL appears to be the most affected lipoproteien fraction in type V and there is 3fold increase in synthesis rate as well as decreased fractional catabolism of VLDL.
Genetics
Precise genetic patterns have not been determined for type V HLP and it has been suggested that type V may be due to number of genetic defects. Among them, the apo E and its isoforms may have an important clinical significance in type V HPL and may affect the catabolism of triglyceride rich lipoproteins. The presence of apo E4 allele may be the genetic factor that predisposes to the development of type V due to delayed lipoprotein clearance.
Associated Conditions
Type V HPL is associated with insulin-dependent diabetes mellitus, alcohol abuse, glycogen storage disease type I, Hyperuricemia, Pancreatitis and xanthomatosis.
Causes
Causes of type V hyperlipoproteinemia is more complicated and more closely related to acquired environmental factors. It rarely shows familial occurrence, but its inheritance is variable. Therefore, type V HLP is usually considered to be triggered by acquired environmental factors in individuals with some congenital susceptibility to altered triglyceride metabolism (genetic factors). While the inovolved environmental factors vary, involvement of heavy dirinking, type 2 Diabetes, hormonal therapy and medications are frequently observed.
Epidemiology and Demographics
Average triglyceride levels in type V hyperlipoproteinemia are lower for women than for men before age 50.
Risk Factors
Screening
Natural History, Complications and Prognosis
Diagnosis
Diagnostic Criteria
If available, the diagnostic criteria are provided here.
History
A directed history should be obtained to ascertain
Symptoms
"Type symptom here" is pathognomonic of the "type disease name here".
"Type non specific symptoms" may be present.
Past Medical History
Family History
Social History
Occupational
Alcohol
The frequency and amount of alcohol consumption should be characterized.