**1. Introduction**

In this chapter, we discuss the groups of disorders classified as systemic sclerosis mimics. Localized and sometimes generalized skin stiffness is typical for this group of diseases. However, quite incongruous pathogenesis, underlying disease mechanisms and distinct organ involvement are significantly different in these conditions. This chapter describes the pathogenesis, clinical manifestation, histopathology findings, and therapeutic possibilities of the most common diseases that may cause difficulties in the differential diagnosis of systemic sclerosis.
