Cutaneous lupus erythematosus (CLE) is the term doctors use when a disease called lupus erythematosus affects the skin. About two-thirds of patients with lupus will develop CLE. Many patients with CLE also have other organs, such as the heart, lungs, kidney, muscles, and joints, that are also affected by lupus.
Lupus erythematosus is an autoimmune disease that leads to increased inflammation in many parts of the body. The inflammation, or damage, can be caused directly by immune cells or specialized proteins called antibodies that are produced by immune cells. In most patients with lupus, the immune system makes anti-nuclear antibodies (ANA), which are given this term because they stick to the nucleus of normal cells.
Your skin is the largest organ in your body. It is made up of three layers: epidermis, dermis, and subcutaneous fat. The outermost, visible layer of the skin is called the epidermis. The cells that make up the epidermis include squamous cells, basal cells, melanocytes, Merkel cells, and cells of the immune system. The squamous cells in the epidermis produce a material called keratin, which makes the skin strong, waterproof, and provides protection from toxins and injuries.
The dermis is below the epidermis, and it is separated from the epidermis by a thin layer of tissue called the basement membrane. The dermis contains blood vessels and nerves. Below the dermis is a layer of fat called subcutaneous adipose tissue (see picture below).
Lupus erythematosus is caused by a combination of genetic, environmental, and immune system factors, which lead to increased inflammation.
Cutaneous lupus erythematosus can present with a broad range of skin lesions. Doctors divide these skin lesions into three categories or types:
The diagnosis of CLE requires information from a variety of sources including your medical history, a physical examination, blood tests, and a skin biopsy. Your medical team will work collaboratively to gather and share this information in order to determine the correct diagnosis.
A skin biopsy is a procedure where a small sample of tissue is removed and sent to a pathologist for examination under a microscope. The tissue sample can be used to look for inflammation, tissue damage, and abnormal antibodies in the skin.
Common microscopic features of cutaneous lupus erythematosus:
Direct immunofluorescence (DIF) is a test that pathologists perform to look for specific proteins in a tissue sample. Unlike most tissue samples, which are examined using normal light, DIF tissue samples are examined using fluorescent light. This makes it easier for your pathologist to see any abnormal proteins in the sample.
In patients with CLE, tissue samples examined from the DIF test will often show increased amounts of immune system-related proteins in the area of the basement membrane. These proteins include IgG, IgM, IgA, and C3.