2-methylbutyrylglycinuria (2MBG) is an inherited condition in which the body is unable to break down certain proteins. It is classified as an organic acid condition because 2MBG can lead to a harmful amount of organic acids and toxins in the body. Symptoms of the condition vary. If 2MBG is identified early and treatment is begun, individuals with 2MBG can often lead healthy lives.
Organic Acid Conditions
No one knows the exact number of individuals who are affected by 2-methylbutytylglycinuria (2MBG), but it is considered a rare condition. However, it is more common among people with Hmong ancestry. This condition is estimated to occur in every 1 out of 250 to 500 people of Hmong ancestry. In many cases, these individuals never develop signs or symptoms of the condition.
Also known as
- 2-methylbutyryl-CoA dehydrogenase deficiency
- 2-MBCD deficiency
- 2-MBAD deficiency
- Short/branched chain acyl-CoA dehydrogenase deficiency (SBCAD)
Your baby’s doctor may ask you if your baby is showing any of the signs of 2MBG (see Early Signs below). If your baby has certain signs, your baby’s physician may suggest starting immediate treatment.
If your baby’s newborn screening result for 2-methylbutyrylglycinuria (2MBG) was out of the normal range, your baby’s doctor or the state screening program will contact you to arrange for your baby to have additional testing. It is important to remember that an out-of-range screening result does not necessarily mean that your child has the condition. An out-of-range result may occur because the initial blood sample was too small or the test was performed too early. However, as a few babies do have the condition, it is very important that you go to your follow-up appointment for a confirmatory test. Because the harmful effects of untreated 2MBG can occur soon after birth, follow-up testing must be completed as soon as possible to determine whether or not your baby has the condition.
Follow-up testing will involve checking your baby’s urine and blood samples for harmful levels of acids and toxins. Certain acids and toxins build up in the body when a child has an organic acid condition, so studying the amounts of these substances in your baby’s body can help doctors determine if your child has a condition. High levels of C5 acylcarnitine in the blood and organic acids in the urine may be signs that your baby has 2MBG. In some cases, follow-up testing may also include testing a very small sample of skin.
There have been very few reported cases of 2-methylbutyryl glycinuria (2MBG). Of those reported, all of the babies were healthy at birth. Signs of 2MBG often begin in infancy, sometimes as early as a few days after birth. In other cases, signs do not develop until childhood.
Signs of 2MBG include:
- Poor appetite
- Sleeping longer or more often
- Weak muscle tone (also known as hypotonia)
- Delayed growth
- Tight muscles (called spasticity)
- Developmental delays
Many of these signs may occur when your baby eats foods that his or her body cannot break down. They can be triggered by long periods of time without eating, illnesses, and infections.
If your baby shows any of these signs, be sure to contact your baby’s doctor immediately.
When 2-methylbutyrylglycinuria (2MBG) is diagnosed early, treatment can help prevent signs and symptoms. In fact, some children will never need treatment.
The best way to prevent the symptoms of 2MBG is to have a very restricted diet for your child. A dietician or a nutritionist can help you plan a low-protein diet that still gives your baby the nutrients he or she needs for healthy growth.
Your baby’s doctor might recommend special baby formulas and foods designed for children with 2MBG. These formulas will likely need to be continued through adulthood.
In addition, your baby will need to eat often to help prevent your baby from experiencing many of the signs mentioned in the Early Signs section. Illnesses and infections can also trigger these signs.
Supplements and Medications
Your baby’s doctor might prescribe L-carnitine supplements. L-carnitine is a natural substance, but your baby’s body might not produce enough of it. Taking these supplements can help get rid of harmful substances in your baby’s body. Your baby’s doctor will need to write you a prescription for these supplements.
If 2-methylbutyrylglycinuria (2MBG) is treated early, your baby can have healthy growth and development.
It is important to get screened and start treatment early. If 2MBG is not treated, children could develop breathing problems, seizures, coma, or brain damage.
When we eat food, enzymes help break it down. Some enzymes break down proteins into their building blocks, called amino acids. Other enzymes break down the amino acids further into their base molecules. In 2-methylbutyrylglycinuria (2MBG), the enzyme 2-methylbutyryl-CoA dehydrogenase is not working correctly.
This enzyme’s job is to break down the amino acid isoleucine for energy. If your baby has 2MBG, your baby’s body does not make enough or makes non-working 2-methylbutyryl-CoA dehydrogenase. When this happens, your baby’s body cannot break down isoleucin, which causes harmful organic acids build up.
2MBG is an autosomal recessive genetic condition. This means that a child must inherit two copies of the non-working gene for 2MBG, one from each parent, in order to have the condition. The parents of a child with an autosomal recessive condition each carry one copy of the non-working gene, but they typically do not show signs and symptoms of the condition. While having a child with 2MBG is rare, when both parents are carriers they can have more than one child with the condition. Learn more about autosomal recessive inheritance.
Support for 2-Methylbutyrylglycinuria
Support groups can help connect families who have a child or other family member affected with 2-methylbutyrylglycinuria (2MBG) with a supportive community of people who have experience and expertise in living with the condition. These organizations offer resources for families, affected individuals, health care providers, and advocates:
Work with your baby’s doctor to determine the next steps for your baby’s care. Some children with 2-methylbutytylglycinuria (2MBG) have severe signs and symptoms while others may never develop them at all. The type of care your child needs depends on whether they develop signs and symptoms. Your baby’s doctor may work with a metabolic doctor and a dietician to provide care for your baby. Some children with 2MBG have developmental delays. If you think that your baby is not meeting his or her developmental milestones, ask your baby’s doctor about the next steps in accessing a developmental evaluation and care.
Because 2MBG is a genetic condition, you may want to talk with a genetics specialist. A genetic counselor or geneticist can help you understand the causes of the condition, discuss genetic testing for 2MBG, and understand what this diagnosis means for other family members and future pregnancies. Speak with your baby’s doctor about getting a referral. The Clinic Services Search Engine offered by the American College of Medical Genetics and Genomics and the Find a Genetic Counselortool on the National Society of Genetic Counselors website are two good places for you or your baby's health care provider to use in identifying local specialists.
At this time we have not located a family story for this particular condition. If your family is affected by 2-methylbutyrlglycinuria (2MBG) and you would like to share your story, please contact us so other families may benefit from your experience.
Each family's experience with a condition is unique, but there are some parts of the evaluation and treatment of 2MBG that are similar to other organic acid conditions. You may find it useful to read the stories of families affected by other organic acid conditions. You can read these stories at the Organic Acidemia Association's website.