Linear Focal Elastosis and PXE-Like Fibroelastolytic-Elastotic Papulosis Disorders

Elastic tissue disorders are heterogeneous and are characterized by increased or decreased dermal elastic tissue. The disorders are further defined by characteristic clinical morphologies and distributions, presence or absence of extracutaneous associations, and distribution and morphology of the elastic tissue alteration. Pseudoxanthoma elasticum (PXE) is an inherited elastic tissue disorder characterized by yellowish papules coalescing into cobblestone plaques on the neck and flexural skin, with increased calcified clumped elastic tissue on biopsy and associated cardiac and ophthalmologic abnormalities. PXE-like disorders that lack systemic associations and calcification of elastic fibers may mimic PXE. These include PXE-like papillary dermal elastolysis (PXE-PDE), white fibrous papulosis of the neck (WFPN), and papillary dermal elastosis (PDE), all of which show elastic tissue loss in the papillary dermis (elastolysis), with variably increased dermal collagen. These are collectivly referred to as fibroelastolytic papulosis (FEP) disorders and are briefly covered in the elastolysis chap. 13 as well. Late-onset focal dermal elastosis (LOF9DE) also presents with PXE-like papules but shows increased reticular dermal elastic fibers. FEP disorders may also have increased elastic tissue; thus, the term fibroelastolytic and elastotic papulosis (FEEP) acknowledges this histologic variability and allows the inclusion of LOFDE in this clinical-pathologic spectrum of elastic tissue disorders. Linear focal elastosis, also characterized by increased dermal elastic fibers, is distinguished by cutaneous horizontal linear bands across the lower and mid spine. This chapter will discuss the clinical and histopathologic features of these disorders.