R50- vs T88.3-
R50 and T88.3 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.
Fever of other and unknown origin
- Chapter 18
- Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
- Section
- R50-R69
Malignant hyperthermia due to anesthesia
- Chapter 19
- Injury, poisoning and certain other consequences of external causes
- Section
- T80-T88
- Hyperpyrexia › malignant, due to anesthetic
- Hyperthermia › malignant, due to anesthesia
- Complication › anesthesia, anesthetic › hyperthermia, malignant
- Complication › anesthesia, anesthetic › malignant hyperthermia
These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027