Overview
TMEM199-CDG (also known as TMEM199-Congenital Disorder of Glycosylation or CDG type IIp) is an extremely rare inherited metabolic condition caused by changes in the TMEM199 gene. This gene provides instructions for making a protein that helps maintain the proper acidic environment inside a part of the cell called the Golgi apparatus. When this protein does not work correctly, the process of glycosylation — which is how sugars are attached to proteins and fats in the body — does not function properly. This sugar-attachment process is essential for many body functions. People with TMEM199-CDG typically have liver involvement, which can show up as mildly elevated liver enzymes in blood tests, elevated cholesterol, and low levels of a protein called ceruloplasmin (which carries copper in the blood). Some patients may also have mildly elevated alkaline phosphatase. Importantly, many affected individuals have relatively mild symptoms compared to other types of CDG, and some may have few noticeable symptoms in daily life. Fatty liver (hepatic steatosis) has been reported in some cases. There is currently no cure or specific treatment for TMEM199-CDG. Management focuses on monitoring liver function and addressing any symptoms that arise. Because this condition is so rare, with only a handful of patients described in the medical literature, our understanding of the full range of symptoms and long-term outcomes is still evolving. Patients benefit from being followed by metabolic specialists and hepatologists who are familiar with congenital disorders of glycosylation.
Also known as:
Key symptoms:
Elevated liver enzymes in blood testsFatty liverElevated cholesterol levelsLow ceruloplasmin levels in the bloodElevated alkaline phosphataseMildly enlarged liverLow copper levels in the bloodAbnormal glycosylation patterns on blood tests
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Variable
Can begin at different ages, from infancy through adulthood
Treatments
No FDA-approved treatments are currently listed for TMEM199-CDG.
View clinical trials →Clinical Trials
View all trials with filters →No actively recruiting trials found for TMEM199-CDG at this time.
New trials open frequently. Follow this disease to get notified.
Specialists
View all specialists →No specialists are currently listed for TMEM199-CDG.
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 TMEM199-CDG.
Community
No community posts yet. Be the first to share your experience with TMEM199-CDG.
Start the conversation →Latest news about TMEM199-CDG
No recent news articles for TMEM199-CDG.
Follow this condition to be notified when news becomes available.
Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
Rare disease caregiving can be isolating. Connect with counseling and peer support.
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.How often should my liver function and blood tests be monitored?,Are there any dietary changes that could help manage symptoms like elevated cholesterol or fatty liver?,Should I be concerned about any long-term complications that might develop over time?,Are there any medications or supplements I should avoid because of this condition?,Is there any ongoing research or clinical trials for TMEM199-CDG that I could participate in?,Should other family members be tested for this condition?,How will this condition be monitored as I (or my child) gets older?
Common questions about TMEM199-CDG
What is TMEM199-CDG?
TMEM199-CDG (also known as TMEM199-Congenital Disorder of Glycosylation or CDG type IIp) is an extremely rare inherited metabolic condition caused by changes in the TMEM199 gene. This gene provides instructions for making a protein that helps maintain the proper acidic environment inside a part of the cell called the Golgi apparatus. When this protein does not work correctly, the process of glycosylation — which is how sugars are attached to proteins and fats in the body — does not function properly. This sugar-attachment process is essential for many body functions. People with TMEM199-CDG t
How is TMEM199-CDG inherited?
TMEM199-CDG follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.