Clinical and Histopathological Characteristics of Acquired Inflammatory Blaschko-Linear Disorders.

Introduction: Acquired inflammatory Blaschko-linear dermatoses have not been studied extensively. Descriptive studies on segmental vitiligo have yielded insights helpful in counseling patients. Similar insights are expected from studies on other acquired inflammatory Blaschko-linear diseases.

Materials and methods: Consecutive patients with an acquired inflammatory Blaschko-linear disease presenting to the dermatology outpatient department of the study center were recruited in a case series. Detailed history and examination, clinical photographs, and histopathological findings were recorded and analyzed. Features were compared between linear and generalized forms to look for any differences.

Results: Out of 99 patients, linear lichen planus (n = 47), linear morphea (n = 31), and lichen striatus (n = 9) were observed most commonly. Skin lesions were present in multiple lines in 52 (52.5%). In 12 (12.1%), more than one anatomical site was involved. In 10 (10.1%), two different Blaschko-linear diseases were seen, and in 3 (3.1%) both diseases occurred in the same/adjacent segments. The disease extended from one or both ends in 64 (88.9%). Nineteen (19.2%) had both linear and generalized disease, with linear lesions being more severe than the generalized lesions (P = 0.038133). Some (18/47, 38.3%) linear lichen planus cases showed prominent atrophy since the onset and formed a distinct subset, predominantly over the head and neck site (P < 0.00001). Histopathology of linear lichen planus differed from controls with generalized lesions in terms of having deeper infiltrate (P = 0.000124), and multi-focal, rather than confluent, lichenoid infiltrates. Atrophy was noted from the onset in 13/31 (41.9%) cases of linear morphea.

Limitations: Limitations include cross-sectional design and lack of controls with generalized nonlinear diseases.

Conclusions: Acquired inflammatory Blaschko-linear disorders show distinct characteristics like involvement of multiple lines and sites, directional progression, and atrophic variants. These can be used for differentiating among different Blaschko-linear diseases, monitoring progression, and counseling patients.