By: PAUL J DEMARCO, MD, FACP, FACR, RHMSUS
Scleroderma is the most unique set of disorders in Rheumatology; this group of diseases bears the distinct common pathway of autoimmune involvement that ends in hardening, or “sclerosis,” of the skin. Sclerosis is caused by the proliferation of a type of cells called fibroblasts, which are cells that make collagen and other thick connective tissue components. These are activated by the immune system but act along a separate pathway to cause disease. The scleroderma disease group can affect all ages and are usually classified in the same manner in children and adults. Scleroderma can be divided into two major groups. One group manifests a fibrotic response primarily in the skin in a localized way and the other group manifests a fibrotic response in a more generalized or systemic manner including the skin. Systemic involvement including sclerosis of internal organs is called systemic sclerosis.
Not all sclerotic disease states are autoimmune. Rheumatologists are particularly skilled in differentiating autoimmune from non-autoimmune sclerotic states. We accomplish this by interpreting the clinical response in the setting of specific autoantibodies (antibodies against our own tissues). There are a variety of examples of non-autoimmune sclerotic or fibrotic disorders.
Certain endocrine diseases such as diabetes can cause a fibrotic disorder in the skin. Medications have been known to cause sclerotic responses in the skin. One example is the contrast agent used for MRI imaging (gadolinium), now known to infiltrate the skin of patients with kidney disease and result in a sclerotic disorder called nephrogenic systemic fibrosis. Another example is a tainted over-the-counter supplement, L-Tryptophan, which was noted to have caused another type of skin thickening known as eosinophilia myalgia syndrome. This article discusses the group of disorders rheumatologists identify as having an autoimmune etiology, that being localized scleroderma and systemic sclerosis.
Localized scleroderma is the group of diseases that manifest only in the skin. A patch of skin with a fibrotic reaction is typically called morphea. It can appear as a single patch or a group of patches; the group of morphea patches is called guttate morphea. This can occur across large regions of the trunk in a symmetrical manner, called generalized morphea. A broader band of sclerodermatous involvement of skin, usually crossing a joint line or an organ system (such as the face or head) is called linear scleroderma. Localized scleroderma is associated with an autoantibody, DNA topoisomerase II, defining localized scleroderma as a rheumatologic or autoimmune disorder.