Testicular Regression Syndrome

 

Features of the syndrome:

(1) karyotype 46 XY

(2) external genitalia may be male, ambiguous or female. A person with one affected testis should have male genitalia.

(3) one or both testes may be involved

(4) dissection with histology discloses one of the following:

(4a) absent testis with rudimentary epididymis and/or vas deferens and/or vascular supply

(4b) fibrous nodule or streak gonad, often with calcifications and/or hemosiderin deposits

(4c) rudimentary testis

 

where:

• If vas and epididymis are found within the scrotum, and the testis is not found in the scrotum or inguinal canal, then it can be assumed that the testis is absent (Smith, 1991, page 271).

 

The causative event may occur in the embryonic or fetal periods, in the perinatal period or soon after birth. Torsion with infarction may be one of the more common causes.

 

Timing of Causative Event Affecting Both Testes

 

The pattern of external genitalia, Mullerian duct, and Wolffian duct structures can help identify the time period during development that the injury occurred.

External Genitalia	Mullerian Duct	Wolffian Duct	Days after Fertil-ization	Proposed Terms for Testicular Regression
female	absent	absent	< 43	early embryonic
female	present	absent	43 - 59	late embryonic
ambiguous	present	absent	60 - 69	early fetal (a)
ambiguous	present	present	70 - 75	early fetal (b)
ambiguous	absent	absent	75 - 84	early fetal (c)
ambiguous-to-male	absent	present	90 - 120	midfetal
male	absent	present	> 140	late fetal

after Table 5, page 48, Coulam (1979)

 

where:

• In the male fetus, the Mullerian ducts begin to degenerate at about 8 weeks after the mother's last menstrual period (about 6 weeks after fertilization) and are completely regressed at 10 weeks (Josso and Briard, 1980, page 202).

• The Wolffian ducts do not initially require testosterone for development but become androgen-dependent when the kidney takes over renal function. Exposure to testosterone then results in "stabilization" of the ducts, so that they do not disappear if testosterone is subsequently withdrawn (Josso and Briard, 1980, page 202).

• I am confused by the Wolffian duct data in the table at 70-75 days and 90-120 days.

• I don't know why the late fetal term should not be > 120 rather than > 140 as in the table.

 

Proposed Terms for Testicular Regression	Previous Terms
early embryonic	pure gonadal dysgenesis
late embryonic	Swyer syndrome
early fetal (a)	true agonadism
early fetal (b)	testicular dysgenesis
early fetal (c)	embryonic testicular regression
midfetal	rudimentary testis
late fetal	vanishing testis; complete bilateral anorchia

after Table 5, page 48, Coulam (1979)