Overview
46,XY difference of sex development (DSD) due to testicular 17,20-desmolase deficiency is a rare hormonal condition that affects people who are genetically male (have XY chromosomes) but whose bodies cannot properly make certain sex hormones. The problem lies in an enzyme called 17,20-desmolase (also known as 17,20-lyase), which is part of a larger protein called CYP17A1. This enzyme is needed to convert certain hormones into androgens — the hormones responsible for typical male sexual development. When this enzyme does not work correctly, the body cannot produce enough androgens during fetal development, which means the genitals may not develop in a typical male pattern. This condition is sometimes called isolated 17,20-lyase deficiency or CYP17A1 17,20-lyase deficiency. People with this condition are born with XY chromosomes but may have genitals that appear female, ambiguous (not clearly male or female), or only partially masculinized. The internal reproductive organs (testes) are usually present but may be undescended. At puberty, the body still cannot make enough sex hormones, so puberty may not progress normally without treatment. Treatment focuses on hormone replacement therapy to support normal development and quality of life. Decisions about gender assignment, surgery, and hormone therapy are deeply personal and are made carefully with a team of specialists. With proper medical care, many people with this condition can live full and healthy lives.
Key symptoms:
Genitals that appear female or ambiguous at birth in a person with XY chromosomesUndescended testes (testes located in the abdomen or groin rather than the scrotum)Absence of a uterus and ovaries (internal organs are male despite external appearance)Delayed or absent puberty without treatmentNo development of pubic or underarm hair at pubertyInfertilityLow levels of male sex hormones (androgens) in blood testsNormal or elevated levels of certain precursor hormones (like progesterone and pregnenolone)Normal blood pressure (unlike the related 17-hydroxylase deficiency)Normal salt balance in the body
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for 46,XY difference of sex development due to testicular 17,20-desmolase deficiency.
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Specialists
View all specialists →No specialists are currently listed for 46,XY difference of sex development due to testicular 17,20-desmolase deficiency.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to 46,XY difference of sex development due to testicular 17,20-desmolase deficiency.
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What hormone treatments are available, and when should we start them?,What are the risks of leaving undescended testes in place, and should surgery be considered?,How will we monitor hormone levels over time, and how often do we need check-ups?,What support is available for questions about gender identity and emotional wellbeing?,Are there any fertility options we should know about, even if they are limited?,Should other family members be tested for this gene change?,Are there any clinical trials or research studies we could participate in?
Common questions about 46,XY difference of sex development due to testicular 17,20-desmolase deficiency
What is 46,XY difference of sex development due to testicular 17,20-desmolase deficiency?
46,XY difference of sex development (DSD) due to testicular 17,20-desmolase deficiency is a rare hormonal condition that affects people who are genetically male (have XY chromosomes) but whose bodies cannot properly make certain sex hormones. The problem lies in an enzyme called 17,20-desmolase (also known as 17,20-lyase), which is part of a larger protein called CYP17A1. This enzyme is needed to convert certain hormones into androgens — the hormones responsible for typical male sexual development. When this enzyme does not work correctly, the body cannot produce enough androgens during fetal
How is 46,XY difference of sex development due to testicular 17,20-desmolase deficiency inherited?
46,XY difference of sex development due to testicular 17,20-desmolase deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does 46,XY difference of sex development due to testicular 17,20-desmolase deficiency typically begin?
Typical onset of 46,XY difference of sex development due to testicular 17,20-desmolase deficiency is neonatal. Age of onset can vary across affected individuals.