Doctors classify the disease into different categories based on the number of enlarged lymph node regions and the underlying cause. There are four established subtypes of Castleman disease:

Unicentric Castleman disease
Unicentric Castleman disease (UCD) involves a single enlarged lymph node or multiple enlarged lymph nodes within a single region of the body that display microscopic features consistent with Castleman disease. It is also sometimes called localized Castleman disease.The exact cause of UCD is unknown, but appears to be due to a genetic change that occurs in the lymph node tissue, most similar to a benign tumor. In most cases of UCD, individuals exhibit no symptoms (asymptomatic). UCD symptoms tend to be mild and occur secondary to compression of surrounding structures by rapidly enlarging lymph nodes. Less commonly, some UCD patients can experience systemic inflammatory symptoms such as fever, fatigue, excessive sweating, weight loss, and skin rash as well as laboratory abnormalities such as low hemoglobin and elevated C-reactive protein. These symptoms are typically seen in MCD. Surgery is considered by experts to be the first-line treatment option for all cases of UCD. Sometimes, removing the enlarged lymph node(s) is not possible. If surgical excision is not possible, treatment is recommended for symptomatic patients. If symptoms are due to compression, then rituximab is recommended. If symptoms are due to an inflammatory syndrome, then anti-interleukin-6 (IL-6) therapy is recommended. If these treatments are not effective, then radiation may be needed.
Pemphigus foliaceus is an autoimmune blistering disease (bullous disorder) of the skin. Pemphigus foliaceus causes a characteristic inflammatory attack at the subcorneal layer of epidermis, which results in skin lesions that are scaly or crusted erosions with an erythematous (red) base. Mucosal involvement is absent even with widespread disease.If there is an autoimmune IgG buildup in the epidermis, then nearly all of the antibodies are aimed against desmoglein 1. The effect of the antibodies and the immunological pathway is most likely one of three mechanisms:

Steric hindrance of the desmoglein 1: The antibody caps off the site for intracellular binding to another keratinocyte. Activation of an endocytic pathway: The antibody activates a pathway which causes an internalization of desmogleïn 1, which in turn causes a loss of adhesion. Disruption of function: In this case, the antibody blocks the desmoglein 1 from being formed into a desmosome. This in turn causes a loss of adhesion with acantholysis as a result. Cause
The National Institute of Arthritis and Musculoskeletal and Skin Diseases describes it like this:
Normally, our immune system produces antibodies that attack viruses and harmful bacteria to keep us healthy. In people with pemphigus, however, the immune system mistakenly attacks the cells in the epidermis, or top layer of the skin, and the mucous membranes. The immune system produces antibodies against proteins in the skin known as desmogleins. These proteins form the glue that keeps skin cells attached and the skin intact.