Q99.2

Billable

Fragile X chromosome

HCC Category Mapping

RxHCCHCC 148 — Mild Intellectual Disabilities

0.000

What This Code Means

A genetic condition where the X chromosome is fragile and prone to breaking, causing intellectual disability and developmental delays, particularly affecting males.

Coding Tips

•This is the most common inherited cause of intellectual disability; always code associated intellectual disability separately if present
•Document the presence of fragile X in family members as this condition is inherited and affects genetic counseling

Clinical Significance

Fragile X syndrome is the most common inherited cause of intellectual disability and autism spectrum disorders, caused by expansion of CGG repeats in the FMR1 gene on the X chromosome. This condition requires comprehensive management including behavioral interventions, educational support, and medical treatment for associated conditions like ADHD, anxiety, and seizures.

Documentation Requirements

✓Genetic testing confirming FMR1 gene CGG repeat expansion
✓Number of CGG repeats if documented
✓Intellectual disability severity documented
✓Autism spectrum behaviors if present
✓Characteristic physical features (long face, large ears, macroorchidism)
✓ADHD or hyperactivity symptoms
✓Anxiety or mood disorders
✓Family history of intellectual disability

Commonly Confused Codes

F84.0 — Autism spectrum disorder may be present but genetic cause is key F70-F79 — Intellectual disability codes are additional, not replacement Q99.8 — Other sex chromosome abnormalities don't involve fragile X specifically Q99.9 — Unspecified when fragile X is confirmed

Code Hierarchy

└Q99Other chromosome abnormalities, not elsewhere classified └Q99.2Fragile X chromosome

└Q99.2Fragile X chromosome