Testicular hypoplasia

Introduction Congenital testicular hypoplasia, also known as seminiferous tubule hypoplasia or primary small testicular disease or Klinefelter syndrome (Klinefelter syndrome). Described by Klinefelter, Reifenstein, and Albright in 1942, it is characterized by small testicles, no sperm, and increased gonadotropin in the urine. In 1959, Jacobs et al found that the patient's sex chromosome was 47,XXY, which is one more X chromosome than normal males. Therefore, this disease is called 47,XXY syndrome. The fundamental flaw is that males have one more X chromosome, and the common karyotype is 47, XXY or 46, XY/47, XXY.

Cause

(1) Causes of the disease

Congenital testicular hypoplasia may be formed during the process of maturation and division of the egg cells. The sex chromosomes are not separated, forming an egg containing two X. If the egg is combined with Y sperm, it forms 47,XXY fertilized eggs. If the spermatogenic cells do not separate during the first maturation and division of XY, the XY sperm is formed, and this sperm can form 47,XXY fertilized eggs in combination with X eggs. It is generally believed that most of the 47,XXY formation eggs are caused by the absence of sex chromosome segregation during mature division.

(two) pathogenesis

So far, there are about 30 karyotypes of this disease. The vast majority of patients have a karyotype of 47,XXY, accounting for 80% of all cases. About 15% of patients have chimeras with 2 or more cell lines, of which 46, XY/47, XXY (about 7%) and 46, XY/48, XXXY chimeric, the former The clinical performance was milder than the typical 47,XXY. Another 1% of patients had a karyotype of 46, XX/47, and XXY, but the phenotype was the same as that of a typical congenital testicular hypoplasia. There are also patients with typical clinical manifestations whose karyotype is 46, XX. The explanation for this strange phenomenon is that the patient was a chimera 46, XX/47, XXY in embryonic development, but the XXY cell line disappeared later, or the proportion of the latter was extremely small and thus was not detected.

In addition to chimeric in vitro, there are many variant types of congenital testicular hypoplasia, such as 48, XXYY, 48, XXXY, 49, XXXXY, 49, XXXYY and so on. The more X chromosomes a patient has, the more severe the mental retardation, the more masculine disorder, and the physical deformity. Some XXXY patients have ulnar and tibiofibular joints, and XXXXY patients also have multiple deformities of the craniofacial and limbs. But no matter how many X chromosomes are added, as long as there is a Y chromosome, its phenotype is male.

an examination

Related inspection

Testicular examination of cremaster reflex chromosome testicular biopsy semen volume

Laboratory examinations must be summarized and analyzed based on objective data learned from medical history and physical examination, from which several diagnostic possibilities may be proposed, and further consideration should be given to those examinations to confirm the diagnosis. It is generally difficult to make a diagnosis before the developmental period, and infertility or sexual dysfunction is the main reason for the patient's visit. The body type is higher, the bilateral testicles are smaller, and the breast hypertrophy on both sides is a typical condition. X small body positive, karyotype is 47, XXY can definitely diagnose. At the same time, prenatal diagnosis or intrauterine diagnosis is an important measure for preventive eugenics.

Differential diagnosis

Need to be identified with the following symptoms:

Testicular enlargement and hardening: Proliferative adrenal cortical remnants in the testicles increase and harden the testes, and most patients have no semen after puberty. This symptom occurs in a rare case of bilateral congenital adrenal hyperplasia. Adrenogenital syndrome, which is a congenital adrenal hyperplasia, is a recessive genetic defect genetic disease. Due to the incomplete synthesis of certain enzymes of adrenocortical hormone, the adrenal gland produces hydrocortisone, pituitary The secretion of ACTH is increased, and the adrenal cortex proliferates and secretes too much androgen, which makes the fetus of the female fetus genital, and the amount of 17-ketone in the urine of the patient increases. Congenital defects in certain adrenal enzymes cause abnormal steroid production. Women cause false hermaphroditism and male genitals are huge.

The disease often needs to be differentiated from hypogonadotropic hypogonadism (HH). The latter testicles are small and soft, the external genitalia and secondary sexual characteristics are poorly developed, male breast development is less common, body is also higher, upper and lower limbs are too long, plasma gonadotropin is reduced, serum T is significantly reduced, fine fine Both the tube and Leydig cells have obvious abnormalities and the karyotype is normal. According to these different characteristics, it can be distinguished from the disease.

Patients with congenital testicular hypoplasia have no abnormalities during childhood, often with abnormalities during puberty or adulthood. The patient's body is taller, the lower limbs are slender, the skin is fine, the pubic hair and beard are scarce, and the mane is often absent. It is a steroid-like type. About half of the patients have breast hypertrophy on both sides. The external genitalia is usually normal male, but the penis is shorter than normal males, and the testicles on both sides are significantly smaller, less than 3cm, hard texture, poor sexual function, no sperm in semen, patients often seek treatment due to infertility or sexual function. Mental development is normal or slightly lower.

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