Cystic fibrosis classification

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Shaghayegh Habibi, M.D.[2]

Overview

Cystic fibrosis may be classified according to CFTR protein function abnormality into 6 classes and includes lack of production (class 1), failure to reach the site of action due to misfolding (class 2), defects in gating (class 3), reduced ion conductance (class 4), abnormally low channel numbers (class 5), and decreased half-life (class 6). Cystic fibrosis classes 1,2 and 3 are the most commonly associated with pancreatic insufficiency.

Classification

Cystic fibrosis may be classified according to CFTR mutation type:

Cystic fibrosis classification according to CFTR protein function abnormality
Class	Type of abnormality	Features
Class 1	Total or partial lack of production of a functional CFTR	Most common mutations (class 2 is the most common mutation worldwide) Associated with pancreatic insufficiency
Class 2	Failure to reach the site of action on the cell surface (due to misfolding of the protein)
Class 3	Defects in gating (fail to open in response to intracellular signal)
Class 4	Reduced ion conductance	Rare mutations Typically do not have pancreatic insufficiency
Class 5	Abnormally low channel numbers (splicing mutations resulting in reduced amounts of CFTR protein)
Class 6	Decreased half-life