Background: Blaschko-Linear Manifestations of Multifactorial Polygenic Diseases (BLMMPD) are rare. Their underlying pathogenesis is not known but genetic mosaicism is supposed to be involved.
Objectives: To describe a series of patients with BLMMPD and to establish a meaningful classification of these manifestations.
Materials & methods: We retrospectively retrieved the records of all the patients with Blaschko-linear lesions followed at our institution between 1994 and 2007. Only well-documented cases of BLMMPD were included.
Results: 17 cases were reviewed (11 men and 6 women, mean age 42 years), and the following diagnoses were established: psoriasis (4 cases), lupus erythematosus (1 case), lichen planus (4 cases), dermatomyositis (1 case), adult-onset lichen striatus (4 cases) and adult-onset blaschkitis (3 cases). Careful analysis allowed us to individualize 4 distinct nosological situations: in "type A" manifestations, patients had isolated Blaschko-linear lesions, either of a disease nosologically characterized in a non-segmental manner ("type Aα", e.g. Blaschko-linear psoriasis) or of a disease defined by its Blaschko-linearity ("type Aβ, e.g. lichen striatus); while in "type B" manifestations, patients had other signs of disease, i.e. either non-segmental skin lesions of the same type ("type Bα", e.g. Blaschko-linear psoriasis plus non Blaschko-linear psoriatic lesions), or distinct cutaneous or extra-cutaneous manifestations ("type Bβ", e.g. Blaschko-linear calcinosis cutis in a patient with otherwise typical dermatomyositis).
Conclusions: We propose a comprehensive classification of BLMMPD in well distinct nosological situations, which should be of help if we wish to elucidate the pathogeny of those complex disorders.
Keywords: lines of Blaschko; mosaicism; skin disease.