Dermatomyositis/polymyositis associated with internal malignancy: a consequence of how neoplasms alter generalized extracellular matrix in the host.

The mechanism of dermatomyositis/polymyositis (DM/PM) is unknown. There are multiple probable trigger mechanisms. Internal malignancy is a specific trigger for some cases of DM/PM. It is known that there are marked changes in the extracellular matrix around tumors and that various fractions of depolymerized glycosaminoglycans enter the circulation. Circulating ECM fractions are known to incorporate in the extracellular matrix (ECM). Skin changes in DM include mucin formation, edema, and atrophy. These are not post inflammatory changes. These changes could be a consequence of the tumor's effect in the generalized ECM. Many factors influence ECM. Infections are another probable trigger for DM/PM. Infections induce extracellular matrix changes. It is likely that a role for infectious agents in DM/PM will eventually be defined. The drug D-penicillamine is also a trigger for DM/PM. Understanding the mechanism of any one trigger might aid in helping define other triggers. Four other cutaneous signs of internal malignancy can be explained by the mechanism used to explain DM/PM.