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  3. L00–L99
  4. L80-L99
  5. Other disorders of skin and subcutaneous tissue in diseases classified elsewhere (L99)

Other disorders of skin and subcutaneous tissue in diseases classified elsewhere (L99)

The ICD-10 code L99 is used to classify various skin and subcutaneous tissue disorders that occur as complications of other underlying diseases. It covers conditions where skin problems arise secondary to systemic illnesses, rather than primary skin diseases.

This group includes diverse conditions such as skin complications related to human immunodeficiency virus (HIV) infection, often called HIV-modified skin disease or disorder of skin due to human immunodeficiency virus infection. It also encompasses skin manifestations linked to Behçet disease, rheumatoid arthritis (rheumatoid neutrophilic dermatitis), systemic sclerosis, and amyloidosis limited to the skin. Other examples are skin disorders associated with metabolic, nutritional, or vascular problems, as well as cutaneous signs of infections like acute Chagas’ disease (Chagas’ exanthem), African trypanosomiasis, and bacterial endocarditis. This code helps medical coders correctly document cutaneous complications that are not primary skin diseases but appear due to systemic illnesses. Knowing these synonyms and related conditions ensures accurate assignment of the ICD-10 code for other disorders of skin and subcutaneous tissue in diseases classified elsewhere, supporting precise clinical communication and billing.

Instructional Notations

Code First

Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.

  • underlying disease, such as:
  • amyloidosis E85

Type 1 Excludes

A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.