Alphabetic Index FY2027

F78.A1

SYNGAP1-related intellectual disability

FY2027Chapter 5: Mental, Behavioral and Neurodevelopmental disorders/F70–F79 Intellectual Disabilities

BillableComplete code, valid to report
Care settingsHome Health Primary · Behavioral HealthIPF Primary · MS-DRG 884IPF Comorbidity · Developmental Disabilities

F78.A1 (also written F78A1) is a billable ICD-10-CM diagnosis code for SYNGAP1-related intellectual disability. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 2 codes in category F78 (Other intellectual disabilities). The Alphabetic Index lists it under 4 entries. Its coding notes include a Code first instruction, a Code also instruction, 1 Excludes1 entry and 1 Excludes2 entry.

Code first

If the underlying condition listed here is present and known, sequence it first.

Also from chapter/block level (1 note)
Inherited from F70–F79 Intellectual Disabilities
  • any associated physical or developmental disorders

Code also

Two codes may be needed to describe the condition. This note gives no sequencing order.

This code
  • , if applicable, any associated:
    • autism spectrum disorder (F84.0)
    • autistic disorder (F84.0)
    • encephalopathy (G93.4-)
    • epilepsy and recurrent seizures (G40.-)
    • other pervasive developmental disorders (F84.8)
    • pervasive developmental disorder, NOS (F84.9)

Excludes1

Not coded here. The listed conditions generally should not be reported together.

Also from chapter/block level (1 note)
Inherited from F70–F79 Intellectual Disabilities
  • borderline intellectual functioning, IQ above 70 to 84 (R41.83)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Also from chapter/block level (1 note)
Inherited from Chapter 5 Mental, Behavioral and Neurodevelopmental disorders
  • symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)

Care settings

How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.

Home Health Primary

Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the Behavioral Health clinical group.

Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026

IPF Primary

IPF MS-DRG adjustment. A principal diagnosis of this code groups to this MS-DRG:

MS-DRGDescriptionFactor
884Organic disturbances & intellectual disabilities1.08
A principal diagnosis that groups to none of the 19 designated MS-DRGs gets no MS-DRG adjustment. Otherwise the claim still receives the federal per diem base rate and the other adjustments.

Source: CMS IPF PPS FY 2027 final rule (CMS-1847-F), Addendum A; code lists from the CMS MS-DRG Definitions Manual v44; effective for discharges on or after October 1, 2026

IPF Comorbidity

On the CMS IPF comorbidity list.

Comorbidity categoryFactor
Developmental Disabilities1.04
It counts as a comorbidity when reported as a secondary diagnosis and actively treated during the stay. An IPF receives only one adjustment within a category and can receive adjustments in more than one category.

Source: CMS IPF PPS FY 2027 final rule (CMS-1847-F), Addendum B-3 (comorbidity codes with adjustment factor); effective for discharges on or after October 1, 2026

Includes

Further defines or gives examples of the content of the category.

Also from chapter/block level (1 note)
Inherited from Chapter 5 Mental, Behavioral and Neurodevelopmental disorders
  • disorders of psychological development

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 4 entries