Gonadal Dysgenesis

Introduction

• Description: Gonadal dysgenesis is a developmental abnormality of patients who do not carry the stigmata of Turner syndrome but still have absent menarche because of chromosomal abnormalities. These patients generally are tall (>150 cm), are more normal in appearance, and are a chromosomally heterogeneous group (46,XX, 46,XY, or mosaic X/XY karyotypes).

• Prevalence: Appears in 1/2500 female births. Most common sex chromosome abnormality in females.

• Predominant Age: Present at birth but may not be detected until puberty is delayed.

• Genetics: Sporadic, loss of part or all of one X chromosome (amenorrhea more common with long arm loss; short stature with short arm loss).

Etiology and Pathogenesis

• Causes: Pure gonadal dysgenesis—45,XO (Turner syndrome); 46,XY gonadal dysgenesis (Swyer syndrome); 46,XX q5 X chromosome long-arm deletion, mixed or mosaic (50%).

• Risk Factors: Translocations involving the X chromosome (rare).

Signs and Symptoms

Based on the amount of chromatin lost

• Primary amenorrhea and infertility (the most common cause of failure to begin menstruation is gonadal dysgenesis; in approximately 60% of women with primary amenorrhea, an abnormality of gonadal differentiation or function has occurred during the fetal or neonatal period)

• Absent or grossly abnormal gonad development

Diagnostic Approach