Cutaneous Langerhans cell histiocytosis presenting with hypopigmented lesions: Report of two cases and review of literature.

Langerhans cell histiocytosis is a rare group of disorders that results from the abnormal proliferation and accumulation of dendritic-derived cells in various organs of the body, such as the skin and bones. Hypopigmented macules are a rare cutaneous presentation of Langerhans cell histiocytosis that may pose a diagnostic dilemma when no other findings of Langerhans cell histiocytosis are present at the time of examination. We present 2 cases of the hypopigmented variant of Langerhans cell histiocytosis, including a case with histopathologic features of regression, and a review of the literature.

A molecular mechanism for IL-4 suppression of loricrin transcription in epidermal keratinocytes: implication for atopic dermatitis pathogenesis.

Skin barrier defects play an important role in atopic dermatitis (AD) pathogenesis. Loricrin, an important barrier protein suppressed in human AD, is down-regulated by IL-4 in keratinocytes. However, the molecular mechanism is unknown.

Interleukin-4 Downregulation of Involucrin Expression in Human Epidermal Keratinocytes Involves Stat6 Sequestration of the Coactivator CREB-Binding Protein.

Skin barrier defects play an important role in atopic dermatitis (AD). Involucrin, an important barrier protein suppressed in human AD, is downregulated by interleukin-4 (IL-4). However, the molecular mechanism for IL-4 downregulation of involucrin has not been delineated, and especially how Stat6, a transcriptional activator, represses involucrin expression is unknown.

Interleukin-4 up-regulation of epidermal interleukin-19 expression in keratinocytes involves the binding of signal transducer and activator of transcription 6 (Stat6) to the imperfect Stat6 sites.

Interleukin-19 (IL-19) plays an important role in asthma by stimulating T helper type 2 (Th2) cytokine production. Interestingly, IL-4, a key Th2 cytokine, in turn up-regulates IL-19 expression in bronchial epithelial cells, so forming a positive feedback loop. In atopic dermatitis (AD), another Th2 disease closely related to asthma, IL-19 is up-regulated in the skin.