Down syndrome (Q90) ICD-10-CM
The Q90 code range covers down syndrome with 5 ICD-10-CM diagnosis codes. 4 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Code Also
A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
- associated physical conditions, such as atrioventricular septal defect Q21.2
Use Additional Code
The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an additional code.
Codes in the Q90 Range 5 codes · 4 billable
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the Q90 range.
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)
About the Q90 Code Range
The ICD-10 code Q90 identifies Down syndrome and its specific genetic variations. These codes are used to classify different types of trisomy 21, helping medical coders accurately document the condition according to its underlying cause.
The general code Q90 covers Down syndrome broadly, while Q90.0 specifies Trisomy 21 due to meiotic nondisjunction, also known as "Whole chromosome trisomy meiotic nondisjunction" or "Complete trisomy 21 syndrome." Code Q90.1 represents mosaicism forms caused by mitotic nondisjunction, often referred to as "Trisomy 21 mitotic nondisjunction mosaicism." Q90.2 captures translocation variations, including "Translocation Down syndrome" and "Unbalanced translocation and insertion." The unspecified code Q90.9 is used when the exact type of Down syndrome is not determined, encompassing a range of related terms such as “partial trisomy 21,” “leukemoid reaction in newborns with Down syndrome,” and “dementia due to chromosomal anomaly.” These distinctions in the ICD-10 code for Down syndrome ensure precise documentation for diagnosis, treatment, and epidemiological tracking.
Questions About This Page
How many billable codes are in the Q90 range?
Of the 5 codes in this range, 4 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the Q90 range classify?
The range classifies down syndrome. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
