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Mycosis Fungoides : Pathogenesis

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Pathogenesis of Mycosis Fungoides (MF): The precise pathogenesis of MF is unknown. There is no convincing evidence of genetic predisposition. Familial cases are rare. Higher risk of MF has been associated with certain professions/industries, including farming, painting, woodworking, carpentry, textiles, ceramics, petrochemicals and metal industries.

Long-term exposure to an irritant or an infective agent may have a role in its pathogenesis. The role of many viral and bacterial agents has been investigated but no conclusive evidence has been found to date.

A variety of cytogenetic abnormalities have been detected in MF. They include deletions of chromosomes 1p, 17p, 10q, 13q, and 19, as well as gains of 4/4q, 17q/17, and 18; however, none are specific for MF. The progression from plaque to tumor stage appears to be related to altered functions of tumor suppressor and apoptosis-related genes such as p15, p16, PTEN, and p53. Recurrent mutations have also been detected in genes involved in epigenetic regulation, T-cell receptor signaling, tumor necrosis factor signaling pathway, JAK-STAT signaling pathway, and NF-KB pathway.

Mutations in Fas gene have been documented in MF. This may protect the tumor cells from Fas-mediated apoptosis. Cytotoxic T-cell induce apoptosis via engagement between Fas (expressed on the surface of the target cells) and Fas ligand (FasL). Defects in FasL signaling result in protection against tumor-specific cytotoxic T-cell-mediated immunity.

The image shows erythematous, scaly and eczema-like crusted patches and plaques covering the entire body of this patient with advanced stage MF. Some of the plaques had turned nodular.

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