A relatively large scrotum in a 12-year-old boy may be caused by syringomyelia, inguinal hernia, testicle-related inflammation, testicular tumor, etc. 1. Syringomyelia: If there is too much fluid in the syringomyelia cavity that cannot be absorbed, it will lead to syringomyelia and a relatively large scrotum. 2. Inguinal hernia: This refers to the situation where the sheath is not closed, which may cause the intestines in the abdominal cavity to fall from the sheath into the scrotum, resulting in a larger scrotum. 3. Testicular-related inflammation: Acute orchitis, epididymitis and other related inflammatory conditions may cause the scrotum to become enlarged, usually with pain. 4. Testicular tumors: Testicular tumors usually cause the scrotum to become larger, usually with less pain but with a firmer texture. Parents are advised to take their 12-year-old boy to a professional hospital for examination to confirm the cause of the disease and take appropriate treatment measures.