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Fetal Fragile X Mental Retardation Protein (FMRP) Levels in Lymphocytes

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of a specific protein (FMRP) in your white blood cells (lymphocytes). It helps assess whether you may have Fragile X syndrome, a genetic condition that can cause intellectual disabilities and developmental delays.

Quick summary

["This test helps diagnose Fragile X syndrome by checking for low levels of a key protein linked to the condition."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
64081-3
Short code
FMRP cells/lymph NFr Bld ImStn
Synonyms
FMRP cells/lymph NFr Bld ImStn
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-stain
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you or a family member have symptoms of Fragile X syndrome, such as learning difficulties, speech delays, or behavioral challenges. It may also be used in genetic counseling or research settings to evaluate genetic markers.

What to Expect Before the Test

No special preparation is needed. You’ll provide a small blood sample, usually drawn from your arm. The sample is processed to isolate white blood cells (lymphocytes) for testing.

What the Test Involves

The test analyzes the protein FMRP in your lymphocytes, which are a type of white blood cell. The process may include specialized laboratory techniques to measure protein concentration accurately.

What the Results Mean

Results are qualitative (yes/no) or quantitative (measured levels) and compared to known reference ranges for Fragile X syndrome. Low levels of FMRP strongly suggest the condition, while normal levels do not confirm it.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low FMRP levels in lymphocytes strongly indicate Fragile X syndrome, a genetic disorder caused by a mutation in the FMR1 gene. This mutation leads to reduced production of FMRP, impacting brain development and function. Early diagnosis is crucial for support, counseling, and managing symptoms.

Short name

FMRP Lymphocyte Test

Frequently asked questions

What does a positive or abnormal result mean?
An abnormal result (typically low FMRP levels) suggests Fragile X syndrome. This finding should be confirmed with genetic testing of the FMR1 gene to confirm the mutation. Your healthcare provider will discuss next steps, such as genetic counseling or further evaluation.
What does a normal result mean?
A normal result means your FMRP levels are within expected ranges for this test, but it does not definitively rule out Fragile X syndrome. The condition can sometimes be missed or misdiagnosed without genetic testing. If symptoms persist, further evaluation may be needed.
How often should I get this test?
This test is typically performed once, usually as part of a diagnostic or research evaluation. It is not a routine screening test for the general population. Follow your healthcare provider’s recommendations based on your symptoms or family history.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy