E03.9 vs L98.5
E03.9 and L98.5 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 L98.5
myxedema (E03.9)
E03.9
Hypothyroidism, unspecified
BillableUnspecified
- Chapter 4
- Endocrine, nutritional and metabolic diseases
- Section
- E00-E07
Use when the record says
- Myxedema NOS
Indexed under
- Hoffmann's syndrome
- Hypothyroidism (acquired)
- Myxedema (adult) (idiocy) (infantile) (juvenile)
- Cataract › myxedema (cortical) (immature) (incipient)
- Insufficiency, insufficient › thyroid
L98.5
Mucinosis of the skin
Billable
- Chapter 12
- Diseases of the skin and subcutaneous tissue
- Section
- L80-L99
Use when the record says
- Focal mucinosis
- Lichen myxedematosus
- Reticular erythematous mucinosis
Indexed under
- Mucinosis (cutaneous) (focal) (papular) (reticular erythematous) (skin)
- Reticular erythematous mucinosis
- Scleromyxedema
- Lichen › myxedematosus
- Myxedema › cutis (adult) (idiocy) (infantile) (juvenile)
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