The exact cause of this disease is unknown but an immune-mediated pathogenesis is suspected since affected dogs often have high levels of circulating immune complexes. A familial history is common. Erythemas, scaling, crusting, and ulceration may be seen on the face, tips of the ears, tip of the tail, and periocular area. Oral and footpad lesions can be seen but are rare. Myositis is noted only after the development of skin lesions and can be of variable degree.
Some dogs have only skin lesions.
Diagnosis is based on history, clinical signs and biopsy. The lesions worsen after sun exposure. In some cases no therapy is effective. Cutaneous Epidermotrophic Lymphoma is a T cell lymphoma. It occurs in middle aged animals.