Causes of back nodules include infectious and non-infectious causes. 1. Infectious factors: These include nodules caused by bacteria, fungi, and parasites, such as leprosy, cutaneous porcine cysticercosis, and sporotrichosis. 2. Non-infectious diseases: long back nodules may be suffering from sarcoidosis, cutaneous lymphocytoma, xanthomatosis, rheumatoid arthritis, tuberculosis and so on. In order to find the cause, patients with long back nodules need to do relevant examinations, such as pathology biopsy, local ultrasound, physical examination. Patients with nodules on the back should actively seek medical treatment, in order to avoid further development of the disease, patients should not use their own medication, but under the guidance of the doctor in accordance with standardized treatment.