Why Are AST and ALT Elevated in Duchenne Muscular Dystrophy?

When a child is diagnosed with Duchenne muscular dystrophy (DMD), parents are often confused to hear that a doctor initially suspected a liver problem. The reason for this mix-up is that two specific enzymes—AST (aspartate aminotransferase) and ALT (alanine aminotransferase)—are commonly measured during routine blood work to check liver health. However, these enzymes are not only found in the liver; they are also present in skeletal muscle ^[1].

In DMD, the lack of the protein dystrophin causes muscle cell membranes to become fragile and break down. This allows the AST and ALT inside the muscle cells to leak into the bloodstream ^[2]. When a doctor sees high levels of these enzymes on a blood test, they may initially suspect the liver is damaged, when in fact, the enzymes are coming from the muscles.

The “Liver” Misdiagnosis Delay

It is a recognized possibility for families to experience a delay in a DMD diagnosis because of elevated AST and ALT ^[3]. A doctor might order liver ultrasounds, metabolic tests, or infectious disease panels to find the source of the “liver” problem ^[4]. In rare instances, children have even undergone liver biopsies before the true cause was discovered ^[5].

This happens because AST and ALT are standard parts of a comprehensive metabolic panel, which is a routine blood test. Because they are often referred to as “liver enzymes,” muscle-related elevations can sometimes be overlooked initially ^[1]. In early DMD, both AST and ALT can be severely elevated, sometimes reaching hundreds of units per liter ^[6].

Creatine Kinase (CK): The Key to the Puzzle

The turning point in the diagnostic journey often happens when a doctor checks a creatine kinase (CK) level. CK is an enzyme that is much more specific to muscle breakdown ^[7]. While AST and ALT can indicate issues in either the liver or the muscles, a markedly elevated CK level points strongly toward muscle damage ^[6][8].

In children with Duchenne (and sometimes in symptomatic female carriers ^[9]), CK levels are typically markedly elevated—often many times above the laboratory’s reference range ^[6]. Once a markedly high CK is identified, it supports a muscle source for the abnormal results ^[8][7]. This typically prompts a referral to a neuromuscular specialist and genetic testing to confirm a DMD diagnosis.

In one specific study of male patients referred for unexplained high AST and ALT who also had elevated CK, 47% (85 of 182) were eventually diagnosed with Duchenne or Becker muscular dystrophy ^[10]. This highlights how helpful a CK test can be when AST and ALT are persistently high without a clear liver explanation.

What Do These Tests Mean?

What This Means for Your Child

If your child had elevated AST and ALT during the diagnostic process for Duchenne, it often reflects the muscle breakdown that is the hallmark of DMD. However, children with DMD can still develop unrelated liver issues, so the care team will look at the overall pattern rather than treating normal liver tests as proof that the liver is perfectly fine.

• Other Liver Tests: Doctors will often look at bilirubin and GGT (gamma-glutamyl transferase). These are often normal when AST/ALT elevation is caused primarily by skeletal muscle injury ^[7].
• Levels Change Over Time: You may notice that AST, ALT, and CK levels decrease as your child gets older. This does not mean the DMD is improving; rather, it happens because there is a gradual loss of muscle mass over time, so there is less muscle tissue breaking down and leaking enzymes ^[11][12].
• Monitoring is Individualized: There is no single routine protocol for monitoring CK, AST, or ALT after a DMD diagnosis. Repeat testing depends on the clinical situation, especially if your child starts a new medication that could affect the liver ^[13].

When to Suspect a True Liver Problem

Because your child’s AST and ALT may run high due to their muscles, it is important to know the physical signs of genuine liver distress. Contact your care team promptly if you notice:

• Yellowing of the skin or eyes (jaundice)
• Persistently dark urine or pale stools
• Significant abdominal swelling or pain
• Persistent vomiting
• Unusual bleeding or bruising
• New confusion or severe fatigue

Knowing how to interpret these early blood tests can help alleviate worries, while keeping you prepared for ongoing medical conversations.