[Context and Motivation] KAOS is a goal-based modelling language used to model requirements and has been used in industrial and academic projects. Often, the language has been extended to incorporate new constructs related to an application domain. It will continue to be extended. [Question/Problem] Identifying and choosing existing KAOS extensions based on their constructs and characteristics can be a challenging task due to a great number of the existing KAOS extensions. Thus, a Systematic Literature Review was conducted to identify and analyse KAOS extensions. This paper contributes by identifying and analysing the existing KAOS extensions and their constructs. [Principal Idea/Results] The results point to 50 papers (each one presenting a different KAOS extension) and 221 constructs proposed. The extensions and their constructs were analysed according to well-defined questions in two dimensions: a general analysis and a model-based analysis (to characterise the extensions from semantic and syntactic definitions). The application domains targeted by the KAOS extensions, concepts definition, syntax (abstract or concrete) and details about the abstract and concrete syntaxes’ definitions are presented as results of our analysis. [Contribution] Thus, the analysis of the KAOS extensions and their constructs can be easier the identification and choice of existing KAOS extensions based on their characteristics and constructs. Additionally, a catalogue of KAOS extensions was proposed to support the extenders searching for KAOS extensions and constructs identified by this SLR.