Q100-Q109
Medium Complexity

Chromosomal abnormalities, not elsewhere classified

Primary Specialty: Genetics
Last Updated: 2025-09-10

ICD-10 Codes (0)

0 billable
0 category headers

No codes found matching your search

Updates & Changes

FY 2026 Updates

Current Year

New Codes (1)

Q23.4
Hypoplastic left heart syndrome with mitral atresia

Revised Codes (1)

Q21.0
Ventricular septal defect - updated to include hemodynamic significance when known

Deleted Codes

No codes deleted in this range for FY 2026

Historical Changes

  • FY 2025: Routine maintenance updates with minor terminology clarifications
  • FY 2024: Enhanced specificity requirements for certain code ranges
  • FY 2023: Updated documentation guidelines for improved clarity

Upcoming Changes

  • Proposed updates pending review by Coordination and Maintenance Committee
  • Under consideration: Enhanced digital health integration codes

Implementation Guidance

  • Review all FY 2026 updates for Q100-Q109 codes before implementation
  • Always verify the most current codes in the ICD-10-CM manual
  • Ensure clinical documentation supports the selected diagnosis codes
  • +3 more guidance items...

Range Overview

high priority

The ICD-10 code range Q100-Q109 encompasses chromosomal abnormalities that are not classified elsewhere. These codes are used to document conditions such as Down syndrome, Patau syndrome, and Edwards syndrome. The codes also cover other chromosomal abnormalities, including those that affect the sex chromosomes. These codes are crucial in tracking patient health, managing care, and conducting genetic research.

Key Usage Points:

  • Always code to the highest level of specificity.
  • Use additional codes to identify any associated physical or mental disabilities.
  • When coding sex chromosome abnormalities, consider the patient's phenotypic sex.
  • For mosaic conditions, use the code that corresponds to the predominant phenotype.
  • Always verify the code in the Tabular List before assigning it.

Coding Guidelines

When to Use:

  • When a patient is diagnosed with a chromosomal abnormality.
  • When a chromosomal abnormality is identified during prenatal testing.
  • When a patient presents with symptoms consistent with a known chromosomal abnormality.
  • When a patient's family history includes chromosomal abnormalities.
  • When a patient has a known chromosomal abnormality and is being monitored for associated conditions.

When NOT to Use:

  • When a patient has a chromosomal abnormality that is classified elsewhere.
  • When a patient has a suspected but not confirmed chromosomal abnormality.
  • When a patient has a condition caused by a gene mutation, not a chromosomal abnormality.
  • When a patient's chromosomal abnormality is not relevant to the current encounter.
  • When a patient's chromosomal abnormality has been corrected (e.g., through gene therapy).

Code Exclusions

Always verify exclusions in the Tabular List before assigning a code.

Documentation Requirements

Accurate documentation is crucial for coding chromosomal abnormalities. The documentation should clearly state the specific abnormality, any associated conditions or symptoms, and the patient's phenotypic sex (if relevant).

Clinical Information:

  • Specific chromosomal abnormality
  • Patient's phenotypic sex
  • Associated conditions or symptoms
  • Results of genetic testing
  • Family history of chromosomal abnormalities

Supporting Evidence:

  • Genetic test results
  • Medical history
  • Physical examination findings
  • Consultation notes
Good Documentation Example:

Patient diagnosed with Down syndrome (trisomy 21) based on genetic testing. Presents with intellectual disability and congenital heart disease.

Poor Documentation Example:

Patient has a chromosomal abnormality.

Common Documentation Errors:

  • Not specifying the chromosomal abnormality
  • Not documenting associated conditions or symptoms
  • Not considering the patient's phenotypic sex
  • Not using additional codes when necessary

Range Statistics

9
Total Codes
0
Billable
Complexity:
Medium
Primary Use:Clinical Documentation
Chapter:17

Coding Complexity

Medium
Complexity Rating

Coding chromosomal abnormalities requires a solid understanding of genetics and the ability to interpret complex clinical information. However, once the specific abnormality is known, the coding process is relatively straightforward.

Key Factors:
  • Understanding the specific chromosomal abnormality
  • Identifying associated conditions or symptoms
  • Considering the patient's phenotypic sex
  • Using additional codes when necessary
  • Verifying the code in the Tabular List

Specialty Focus

These codes are primarily used by geneticists, pediatricians, and obstetricians. They may also be used by other specialists who treat conditions associated with chromosomal abnormalities.

Primary Specialties:
Genetics
40%
Pediatrics
30%
Obstetrics
30%
Clinical Scenarios:
  • A patient is diagnosed with Down syndrome based on genetic testing.
  • A patient with Turner syndrome presents with short stature and delayed puberty.
  • A patient's prenatal testing reveals trisomy 18 (Edwards syndrome).
  • A patient with Klinefelter syndrome is being monitored for breast cancer.
  • A patient with a family history of chromosomal abnormalities is undergoing genetic counseling.

Resources & References

There are numerous resources available for coding chromosomal abnormalities, including the official ICD-10 coding guidelines, genetic databases, and educational materials.

Official Guidelines:

  • ICD-10-CM Official Guidelines for Coding and Reporting
  • World Health Organization's International Classification of Diseases
  • National Center for Biotechnology Information's Genetic Testing Registry

Clinical References:

  • American Journal of Medical Genetics
  • Genetics in Medicine
  • Nature Reviews Genetics

Educational Materials:

  • American Health Information Management Association's coding resources
  • American Academy of Professional Coders' coding training
  • Centers for Disease Control and Prevention's information on genetic disorders

Frequently Asked Questions

How do I code a mosaic chromosomal abnormality?

For mosaic conditions, use the code that corresponds to the predominant phenotype. If the phenotype is not clear, consult the patient's geneticist or use a general code for chromosomal abnormalities.