Hypolipoproteinemia

Lipid Disorders Main Page
Overview
Causes
Classification Abetalipoproteinemia Hypobetalipoproteinemia Familial hypoalphalipoproteinemia LCAT Deficiency Chylomicron retention disease Tangier disease Familial combined hypolipidemia
Differential Diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohamed Moubarak, M.D. [2]; Aravind Kuchkuntla, M.B.B.S[3]; Tarek Nafee, M.D. [4]

Synonyms and keywords: Hypolipidemia, low lipoprotein

Overview

Hypolipoproteinemia is defined as low levels of one or more type of lipoproteins. Hypolipidemia, a commonly used term in the clinical practice, describes low level of lipids, whether cholesterol or triglycerides. They are referred to as hypocholesterolemia and hypotriglyceridemia respectively. Despite being commonly used to describe abnormalities in lipid metabolism, the term hypolipidemia is not very specific. For instance, people who have metabolic syndrome have high LDL and low HDL and yet they are described to have hyperlipidemia when their HDL level is decreased. Moreover, some people who have low levels of a specific lipoprotein may have a normal measured total cholesterol and triglyceride levels.

Classification

Shown below is an algorithm depicting the classification of hypolipoproteinemia into primary and secondary.

Hypolipoproteinemia

Primary (Genetic)

Secondary

Abetalipoproteinemia Apolipoprotein 1 deficiency Chylomicron retention disease Familial combined hypolipidemia Hypobetalipoproteinemia LCAT deficiency Primary alphalipoproteinemia PCSK9 deficiency Tangier disease

Anemia Criticial illness Chronic inflammation Chronic liver disease Hyperthyroidism Infection Malabsorption Malignancy

Approach to Low Cholesterol Level

Low LDL C <5th percentile or HDL <20mg/dl

Clinical symptoms Diarrhea±Vomiting±Failure to Thrive

If No, then screen for LCAT deficiency, Apo A1 deficiency, Tangier Disease or Heterozygous HBL

If Yes, Screen for secondary causes of low cholesterol as they are more common

Once the secondary causes of low cholesterol are ruled out then consider screening for Abetalipoproteinemia, Chylomicron Retension Disease and Familial Combined Hypolipidemia

Lipid panel: Low LDL C with normal Triglyceride level

Suggests Chylomicron Retention Disease, confirm diagnosis by endoscopy and gene sequencing

Low LDL C with Low Triglyceride can be Abetalipoproteinemia or Homozygous hypobetalipoprotienemia

Screen the lipid panel of the patient's parents

Normal Lipid level suggests Abetalipoproteinemia, confirm diagnosis with gene sequencing

Lipid levels 50% of normal, it is Familial Homozygous Hypobetalipoproteinemia, confirm by gene sequencing

Low LDL C

• It is defined as patients having LDL C less than the 5th percentile when compared to normal population.
• We have to rule out secondary causes first and then consider screening for rare genetic diseases.

	Abetalipoprotienemia	Familial Homozygous Hypobetalipoproteinemia	Familial Heterozygous Hypobetalipoproteinemia	PCSK9 deficiency	Chylomicron Retention Disease	Familial Combined Hypolipidemia
LDL C	↓↓↓ (0)	↓↓↓	↓	↓	↓↓	↓↓
Apo B	↓↓↓( 0)	↓↓↓	↓	N	↓↓	N
TG	↓↓↓	↓↓↓	↓	↓	N	↓
TC	↓↓↓	↓↓↓	↓	↓	↓↓	↓
HDL	↓↓	↓↓	N	N	↓↓	↓↓
VLDL	↓↓	↓↓	↓	N	↓↓	↓
Apo A1	↓↓	↓↓	↓	N	↓↓	N