2026 ICD-10-CM Diagnosis Code Q90.9Down syndrome, unspecified

ICD-10-CM Codes›Q00-Q99›Q90-Q99›Q90

ICD-10-CM Q90.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q90.9 is a billable ICD-10-CM diagnosis code for down syndrome, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Chromosomal abnormalities.

Code Identity

ICD-10-CM Code
Q90.9
Billable Status
Yes — Valid for Submission
Code Describes
Down syndrome, unspecified
Short Description
Down syndrome, unspecified
Same as the full description in the CMS dataset.
Parent Code
Q90
Down syndrome

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ90-Q99Chromosomal abnormalities, not elsewhere classified
CategoryQ90Down syndrome
This CodeQ90.9Down syndrome, unspecified

Present on Admission (POA)Billing

Q90.9 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • 21q partial distal trisomy
  • 21q partial trisomy
  • Complete trisomy 21 syndrome
  • Dementia due to chromosomal anomaly
  • Dementia with Down syndrome
  • Distal duplication of chromosome 21
  • Down syndrome co-occurrent with leukemoid reaction associated transient neonatal pustulosis
  • Down's facies
  • Leukemoid reaction
  • Leukemoid reaction of the newborn
  • Myeloid leukemia associated with Down syndrome
  • Partial trisomy 21 in Down's syndrome
  • Partial trisomy of chromosome 21
  • Periodontitis exacerbated by Down syndrome
  • Proximal duplication of chromosome 21
  • Transient abnormal myelopoiesis
  • Transient abnormal myelopoiesis co-occurrent with Down syndrome
  • Transient neonatal pustulosis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Trisomy 21 NOS

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Down syndrome
    • Syndrome
      • Down
    • Syndrome
      • trisomy
        • 21
    • Trisomy(syndrome)
      • 21 (partial)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MAL009
Chromosomal abnormalities
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Down Syndrome

    a chromosome disorder associated either with an extra chromosome 21 or an effective trisomy for chromosome 21. clinical manifestations include hypotonia, short stature, brachycephaly, upslanting palpebral fissures, epicanthus, brushfield spots on the iris, protruding tongue, small ears, short, broad hands, fifth finger clinodactyly, single transverse palmar crease, and moderate to severe intellectual disability. cardiac and gastrointestinal malformations, a marked increase in the incidence of leukemia, and the early onset of alzheimer disease are also associated with this condition. pathologic features include the development of neurofibrillary tangles in neurons and the deposition of amyloid beta-protein, similar to the pathology of alzheimer disease. (menkes, textbook of child neurology, 5th ed, p213)

  • Leukemoid Reaction

    a peripheral blood picture resembling that of leukemia or indistinguishable from it on the basis of morphologic appearance alone. (dorland, 27th ed)

  • Leukemoid Reaction

    a hematology test result that indicates the presence of an increased white blood cell count and increased neutrophil precursors resembling leukemia, in a peripheral blood smear.

  • Transient Leukemoid Reaction of the Newborn|Leukemoid Reaction of the Newborn|Transient Leukemoid Reaction of Newborn

    increased white blood cell count and increased neutrophil precursors resembling leukemia in a neonate or fetus. often, this is a response to medications received, infection or down syndrome.

Patient EducationClinical

Down Syndrome

Down syndrome is a condition in which a person has an extra chromosome or an extra piece of a chromosome. This extra copy changes how a baby's body and brain develop. It can cause both mental and physical challenges during their lifetime.

The full article covers:

  • What is Down syndrome?
  • What causes Down syndrome?
  • What are the symptoms of Down syndrome?
  • What other problems does Down syndrome cause?
  • How is Down syndrome diagnosed?
  • What are the treatments for Down syndrome?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert Q90.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
758.0 Down's syndrome
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Q90.9Overview

Is Q90.9 (Down syndrome) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report down syndrome, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is Q90.9 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for down syndrome, unspecified on inpatient claims.

What is the ICD-9 equivalent of Q90.9?

Under the General Equivalence Mappings, down syndrome, unspecified converts to ICD-9-CM 758.0 (Down's syndrome). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.