Alphabetic Index FY2027

T78.41

Arthus phenomenon

FY2027Chapter 19: Injury, poisoning and certain other consequences of external causes/T66–T78 Other and unspecified effects of external causes

Non-billable headerNot valid on its own. Use one of the more specific codes under it.

T78.41 is a non-billable ICD-10-CM code header for arthus phenomenon. Report a more specific code from it instead. It is part of the FY2027 code set, effective October 1, 2026. A 7th character is required to complete the code. Its coding notes include a Use additional code instruction, a Code also instruction, 7 Excludes1 entries and 3 Excludes2 entries.

7th character

Category T78 requires a 7th character. T78.41 has only 5 characters, so a placeholder X fills the 6th position.

Assembled code T78.41XA Open code

Guidelines tip

From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.

The 7th character depends on whether the patient is in active treatment, not on who sees the patient. An aftercare Z code is not used for injury aftercare.

Guidelines I.C.19.aInjuries: application of 7th charactersRead the official text

Use additional code

Add the listed code as a secondary code, if known.

Also from chapter/block level (1 note)
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • code to identify any retained foreign body, if applicable (Z18.-)

Code also

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

Also from chapter/block level (6 notes)
Inherited from T66–T78 Other and unspecified effects of external causes
  • , if applicable, place of occurrence, such as:
    • highway rest stop (Y92.523)
    • school (private) (public) (state) as the place of occurrence of the external cause (Y92.21-)
    • service areas as the place of occurrence of the external cause (Y92.52-)
    • single-family non-institutional (private) house as the place of occurrence of the external cause (Y92.01-)
    • transport vehicle as the place of occurrence of the external cause (Y92.81-)

Excludes1

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

Inherited from T78.4 Other and unspecified allergy
  • specified types of allergic reaction such as:
    • allergic diarrhea (K52.29)
    • allergic gastroenteritis and colitis (K52.29)
    • dermatitis (L23-L25, L27.-)
    • food protein-induced enterocolitis syndrome (K52.21)
    • food protein-induced enteropathy (K52.22)
    • hay fever (J30.1)

Excludes2

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

Inherited from T78 Adverse effects, not elsewhere classified
  • complications of surgical and medical care NEC (T80-T88)
Also from chapter/block level (2 notes)
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • birth trauma (P10-P15)
  • obstetric trauma (O70-O71)

Inclusion terms

Conditions classified to this code.

This code
  • Arthus reaction

Notes

Also from chapter/block level (2 notes)
Inherited from Chapter 19 Injury, poisoning and certain other consequences of external causes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 1 entry

7th-character codes under T78.41 3