Blaschko-linear inflammatory dermatosesL44.2

Blaschko-linear inflammatory dermatoses are a group of acquired inflammatory skin diseases that, in an otherwise completely healthy skin, manifest exclusively along Blaschko lines. One example is lichen striatus or "inflammatory linear verrucous epidermal nevus, ILVEN". Another example is the childhood- and adult-acquired clinical pictures known as "Blaschkitis", and more recently "Acquired inflammatory skin eruption" (Raposo I et al 2018) or "Blaschkolinear acquired inflammatory skin eruption" (Aravind M et al 2016). These belong to the disease group of "Blaschkolinear inflammatory dermatoses" (Denk K et al 2011; Müller CS et al 2011), raising the question whether they are different entities or not one and the same clinical picture.

Apparently, Blaschko linear inflammatory mosaic dermatoses are based on an invisible, so to speak dormant, cutaneous mosaic caused by a somatic mutation, which is characterized by a clinically undetectable altered antigen stock. At this point, the skin appears completely normal prior to the onset of linear disease, although the cutaneous mosaic with its altered genotype exists from birth.

Due to an environmental influence or some other stimulus, the aberrant cell clone can be activated and then manifests as a dermatosis following the Blaschko linear pattern. This particular phenotype is thus determined by the interaction of preexisting (dormant) cutaneous mosaic and activating environmental factors. If the triggering moment ceases, the disease can heal spontaneously or by appropriate therapeutic measures.

Blaschko-linear inflammatory mosaic dermatoses can occur under various manifestations, such as linear lichen planus, linear lichen nitidus, linear (nevoid) psoriasis, linear atopic dermatitis, and other inflammatory skin diseases (Sengupta S et al. 2012). Histologically, they correspond to the phenotype realized in each case (e.g., an interface der matitis in Blaschko-linear lichen planus, or psoriasis in Blaschko-linear psoriasis- Suárez-Peñaranda JM et al. 2017).

Blaschko-linear inflammatory dermatoses arise spontaneously, regardless of age, and surprisingly can heal completely even after years of persistence, equally spontaneously or after forced therapy (Liddell LT et al.2015; Wollina U et al. 2017). They follow the pathogenetic pattern of the underlying dermatosis (e.g., lichen planus).

A stripe-like or a segmental affection superimposed on the otherwise site-typically distributed underlying disease can also be observed in various preexisting polygenic skin diseases such as psoriasis, atopic dermatitis or lichen planus. This phenomenon is probably due to a postzygotic mutation at an additional predisposing gene.

1. Aravind M et al (2016) Blaschkolinear acquired inflammatory skin eruption, or blaschkitis, with features of lichen nitidus.JAAD Case Rep 2:102-104.
2. Denk K et al (2011) Blaschkitis in children - a new entity? J Dtsch Dermatol Ges 9:48-49.
3. Happle R (2018) Mosaicism and epidermal nevi. In: Braun-Falco`s Dermatology, Venerology Allergology G. Plewig et al. (Hrsg) Springer Verlag S 1024-1025
4. Liddell LT et al(2015) Persistent blaschkitis responsive to high potency topical steroids.Dermatol Online J 21: pii: 13030/qt2vg933vz.
5. Müller CS et al (2011) Lichen striatus and blaschkitis: reappraisal of the concept of blaschkolinear dermatoses. Br J Dermatol 164:257-262.
6. Raposo I et al (2018) Adult blaschkolinear acquired inflammatory skin eruption (BLAISE) with simultaneous features of lichen striatus and blaschkitis. Dermatol Online J. 2018 24: pii: 13030/qt6394z6nc.
7. Sengupta S et al (2012) Naevoid Psoriasis and ILVEN: Same Coin, Two Faces? Indian J Dermatol 57:489-491.
8. Suárez-Peñaranda JM et al (2017) Unusual Interface Dermatoses Distributed Along Blaschko's Lines in Adult Patients.At J Dermatopathol 39:144-149.
9. Wollina U et al (2017) ILVEN - COMPLETE REMISSION AFTER ADMINISTRATION OF TOPICAL CORTICOSTEROID (CASE REVIEW). Georgian Med News 263:10-13.