Diagnosing Catalase Deficiency

Diagnosing a rare condition like acatalasemia often involves a journey from a simple bedside observation to highly specialized genetic mapping. Because the condition is so rare, many doctors may not have encountered it before. It is essential to understand the specific tests used to confirm the diagnosis and the potential pitfalls that can lead to incorrect medical conclusions.

The Classic Bedside Clue: The “Bubbling Test”

The most famous way to identify acatalasemia is a simple biochemical observation. Under normal circumstances, when hydrogen peroxide is added to a blood sample, the enzyme catalase immediately breaks it down into water and oxygen ^[1]. This reaction creates a white, foamy bubbling effect.

In someone with acatalasemia, this reaction is missing ^[1]:

• Lack of Foaming: The blood sample will not bubble or foam when hydrogen peroxide is added.
• Color Change: Instead of bubbling, the blood may turn a brownish-black color as the peroxide reacts directly with the hemoglobin ^[1].

While this “bubbling test” is a striking indicator, modern medicine relies on more precise laboratory tools for a definitive diagnosis.

Genetic Mapping: Finding the CAT Mutation

To confirm acatalasemia, doctors look directly at the CAT gene. There are two primary ways they do this:

1. Sanger Sequencing: This is a targeted test used when a doctor specifically suspects a mutation in the CAT gene. It “reads” the gene letter-by-letter to find the exact error ^[2].
2. Whole Exome Sequencing (WES): If a patient has complex symptoms and the cause isn’t clear, doctors may use WES. This test screens all the protein-coding regions of the DNA. It is highly recommended for identifying the biallelic (two-sided) mutations that cause acatalasemia, especially when other tests are inconclusive ^[2].

The HbA1c Trap: A Crucial Warning

The most important thing for patients to know about testing is the HbA1c trap. Hemoglobin A1c (HbA1c) is a common blood test used to screen for diabetes by measuring average blood sugar over three months.

In individuals with acatalasemia, certain HbA1c tests can give a false-high reading ^[3].

• The Mechanism: Some testing kits (such as the NORUDIA N kit) use an enzymatic process to measure HbA1c. These tests rely on chemicals that are sensitive to hydrogen peroxide. Because a person with acatalasemia has “residual” (leftover) peroxide in their blood, it interferes with the test’s chemistry, making the blood sugar appear much higher than it actually is ^[3].
• The Risk: This can lead to being incorrectly diagnosed with diabetes and prescribed unnecessary, potentially dangerous treatments.
• The Solution: If blood sugar needs to be checked, doctors should use alternative methods that do not rely on these specific enzymes. Methods like High-Performance Liquid Chromatography (HPLC) or measuring Glycated Albumin (GA) are generally more reliable for patients with acatalasemia ^[4][5].

Biochemical Activity Testing

Beyond genetics, labs can measure the actual activity level of the catalase enzyme in the blood ^[3]. This helps distinguish between:

• Acatalasemia: Little to no enzyme activity (found in those with two gene mutations) ^[2].
• Hypocatalasemia: Roughly 50% of normal activity (found in those with one gene mutation), which usually does not cause symptoms but can still cause slight interference in laboratory tests ^[3][6].