The BCHE Gene and Diagnosis

Understanding how hereditary butyrylcholinesterase deficiency is diagnosed requires looking at both your blood chemistry and your DNA. Because this condition is asymptomatic (shows no symptoms) in daily life, doctors use specific laboratory tests to “stress test” your enzymes or read your genetic code ^[1][2].

The Genetics: Autosomal Recessive Inheritance

This condition is caused by variations in the BCHE gene, located on chromosome 3 ^[3]. It follows an autosomal recessive inheritance pattern ^[4]. This means:

• Two Copies: To have the most severe form of the deficiency, you typically must inherit two “faulty” copies of the gene—one from your mother and one from your father ^[4][5].
• The Carrier State: If you inherit only one faulty copy, you are a “carrier.” Carriers usually have enough working enzyme to handle anesthesia normally, though they may break down the drugs slightly more slowly than others ^[6][7].

What about my children?

Because this is an inherited condition, your biological children may be affected, particularly if your partner is also a carrier ^[4][1]. Since children often require routine procedures (like tonsillectomies or ear tubes) that involve anesthesia, it is highly recommended to have them tested via a simple blood test or genetic swab before they undergo any surgery ^[8][9].

Biochemical Testing: The Inhibition Numbers

When a doctor suspects this deficiency, they first perform a biochemical phenotype test. This is not a DNA test; instead, it measures how your enzyme behaves in a test tube when exposed to certain “inhibitors.”

The Dibucaine Number

Dibucaine is a local anesthetic that inhibits (stops) the work of normal BChE enzymes.

• Normal Enzyme: Dibucaine will stop about 70–80% of the enzyme’s activity. This is called a “normal Dibucaine Number” ^[2].
• Atypical Enzyme: If you have the “atypical” genetic variant, the enzyme is resistant to dibucaine. It might only be inhibited by 20% ^[8][10].
• Why it matters: A low Dibucaine Number is a “smoking gun” for the atypical variant of the condition ^[2].

The Fluoride Number

Some rare variants are resistant to fluoride instead of dibucaine. Doctors use the Fluoride Number to identify these specific “F-variants,” which also cause prolonged paralysis but might be missed if only dibucaine is used ^[9][11].

Molecular Genetic Testing: The Definitive Map

While biochemical tests tell us how your enzyme acts, molecular genetic testing (DNA sequencing) tells us exactly what your gene is ^[2][8].

Modern guidelines increasingly recommend DNA sequencing because:

1. Precision: It identifies the exact mutation (such as the “Atypical,” “Silent,” or “Kalow” variants), which helps predict exactly how long you might be paralyzed during surgery ^[6][9].
2. Family Planning: It allows for precise testing of family members to see if they are carriers or also at risk ^[1][9].
3. Clarity: It can distinguish between a genetic deficiency and “acquired” deficiency (caused by liver disease or pregnancy), which can sometimes look the same on biochemical tests ^[7][12].

Checklist for Your Diagnostic Report

When you receive your lab results, check to see if they include the following three key components. Having all three provides the most complete picture for your medical record:

If your report is missing any of these, ask your doctor if further testing is needed to ensure you have a “definitive” diagnosis for your records ^[9][2].