Sometimes it is found that a child’s testicles are large on one side and small on the other. Further examination is needed to rule out the presence of syringomyelia, inflammation of one testicle and epididymis, hernia, etc. It is also necessary to rule out testicular dysplasia. Testicular dysplasia may have the following causes: 1, genetic factors: congenital testicular dysplasia is mostly caused by genetic factors – chromosomal abnormalities. A common symptom of chromosomal abnormalities we see is called Creutzfeldt-Jakob syndrome, which has a high incidence. There is also a kind of Kaman’s syndrome, this symptom is due to the abnormality of low sex hormone, which causes the abnormal development of testicles. 2, disease factors: Acquired testicular dysplasia, refers to the patient’s chromosomes are normal, but due to the influence of various pathogenic factors in the fetal period, childhood or early childhood, resulting in abnormal testicular development. For example, some children have mumps, and when this mumps affects the testicles, it may cause viral orchitis, thus causing abnormal development of the testicles. 3. Incomplete testicular descent: The testicles normally develop in the abdominal cavity of the fetus and gradually descend to the scrotum in the last 3 months. When the testicle cannot move into the scrotum normally, it is called incomplete testicular descent, also known as cryptorchidism. It is a common pediatric surgical condition. It occurs in approximately 30% of premature infants and 3% of full-term infants. It is more common unilaterally, on the right side than on the left. Some testes that do not descend at birth are able to descend to the scrotum on their own within a few months, and about 1 in 150 babies never descend to the scrotum.