Is mixed gonadal dysgenesis with 88% Y (Y chromosome) and 12% X (X chromosome) a form of Turner's syndrome?

From the Guidelines

Mixed gonadal dysgenesis with 88% Y and 12% X chromosomes is not a form of Turner syndrome. This condition is characterized by a mosaic karyotype, which is distinct from Turner syndrome, typically involving a complete or partial absence of one X chromosome (45,X or mosaic patterns) 1. The high percentage of Y chromosome material (88%) in this case indicates a predominance of cells with Y chromosome, which is not consistent with Turner syndrome. This condition represents a disorder of sex development where there is asymmetric gonadal development, often with a testis on one side and a streak gonad on the other. Some key points to consider in the management of mixed gonadal dysgenesis include:

• Careful evaluation including imaging of the gonads, assessment of hormone levels, and often gonadal biopsy or removal due to increased risk of gonadoblastoma when Y chromosome material is present 1
• Management typically involves a multidisciplinary team including endocrinologists, urologists, and geneticists to address hormonal needs, fertility concerns, and cancer surveillance
• The risk of gonadoblastoma is a significant concern in patients with mixed gonadal dysgenesis and Y chromosome material, and gonadectomy is often recommended in these cases 1

From the Research

Mixed Gonadal Dysgenesis and Turner's Syndrome

• Mixed gonadal dysgenesis (MGD) is a disorder of sex development caused by mosaicism of the Y chromosome, often represented by 45,X/46,XY 2.
• Turner's syndrome, on the other hand, is typically characterized by a 45,X karyotype without a Y chromosome component.
• The presence of a Y chromosome, even in a mosaic form, increases the risk of malignancy, such as gonadoblastoma, which is not typically associated with Turner's syndrome 3, 4.

Chromosomal Composition and Risk of Malignancy

• A chromosomal composition of 88% Y and 12% X suggests a high risk of malignancy due to the presence of the Y chromosome, similar to MGD 2, 5.
• The risk of gonadoblastoma in individuals with a Y chromosome component is well-documented, and prophylactic gonadectomy is often recommended to mitigate this risk 3, 4, 5.

Diagnosis and Management

• Diagnosis of MGD or other disorders of sex development often involves chromosomal analysis and evaluation of gonadal tissue 2, 4, 6.
• Management may include prophylactic gonadectomy, hormone replacement therapy, and ongoing monitoring for potential complications 2, 3, 4.