Lichen striatus and blaschkitis: reappraisal of the concept of blaschkolinear dermatoses.

BACKGROUND: Blaschkitis (BL) and lichen striatus (LS) are rare dermatoses occurring along the Blaschko lines of the skin with preferential occurrence in distinct age categories. Controversy exists regarding the pathogenesis and classification of BL and LS within the spectrum of blaschkolinear dermatoses.
OBJECTIVES: To describe the clinicopathological characteristics of six cases of BL/LS with special emphasis on immunophenotyping the inflammatory infiltrate. Additionally, we review and critically discuss current concepts of the blaschkolinear dermatoses.
METHODS: Skin biopsies from six patients with BL and LS were analysed retrospectively. The immunophenotypes of the inflammatory cells were determined and related to clinical features.
RESULTS: The clinical characteristics of the diseases occurred equally in both genders and all ages. BL and LS had similar histopathological findings with respect to epidermal changes and composition of the inflammatory infiltrates. Characteristically, a lichenoid lymphocytic infiltrate with exocytosis of inflammatory cells and obvious alterations of the interface zone was observed.
CONCLUSIONS: We characterize the two main blaschkolinear dermatoses BL and LS sensu stricto morphologically and open new insights into the pathogenesis of these diseases. We propose the concept of a wide spectrum of blaschkolinear dermatoses with BL and LS located somewhere within the spectrum. We do not think that it is helpful for clinicians to enlarge the spectrum of blaschkolinear diseases and to create numerous 'new' entities. Rather, our aim was to unify diseases with similar clinical and histopathological features and common genetic pathomechanisms underlying phenotypic variations.