C96.6 vs E88
C96.6 and E88 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on E88
histiocytosis X (chronic) (C96.6)
C96.6
Unifocal Langerhans-cell histiocytosis
Billable
- Chapter 2
- Neoplasms
- Section
- C81-C96
Use when the record says
- Eosinophilic granuloma
- Histiocytosis X, unifocal
- Histiocytosis X NOS
- Langerhans-cell histiocytosis NOS
Indexed under
- Granuloma › eosinophilic
- Histiocytosis › Langerhans' cell NEC
- Histiocytosis › X NEC
- Granuloma › bone › eosinophilic
- Granuloma › bone › lung
E88
Other and unspecified metabolic disorders
Not billable
- Chapter 4
- Endocrine, nutritional and metabolic diseases
- Section
- E70-E88
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