> For the complete documentation index, see [llms.txt](https://docs.snomed.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.snomed.org/snomed-ct-specifications/snomed-ct-editorial-guide/readme/authoring/domain-specific-modeling/clinical-finding-and-disorder/clinical-finding-and-disorder-modeling/specific-clinical-finding-and-disorder-modeling/enzyme-deficiency.md).

# Enzyme deficiency

## Naming and modeling of enzyme deficiencies with genetic and non-genetic etiologies

Enzyme deficiencies may arise from genetic abnormalities or non-genetic mechanisms that reduce the activity or availability of an enzyme.

Where an enzyme deficiency may have either a genetic or non-genetic etiology, the naming pattern `Deficiency of <accepted enzyme name> (disorder)` shall be used for the FSN of an etiologically unspecified concept.

Where the enzyme deficiency concept specifies a gene-caused etiology, the naming pattern `<X> gene-related <Y> deficiency (disorder)` shall be used, where X represents the approved gene name in the FSN and the gene symbol in the PT.  \<Y> represents the affected enzyme accepted name.

### **Modeling requirements**

Where an enzyme deficiency specifies a genetic etiology, the concept **must be modeled using the HAS ASSOCIATED GENE attribute**, with the value representing the gene responsible for the deficiency.

The **HAS ASSOCIATED GENE** relationship shall not be added to an etiologically unspecified enzyme deficiency concept solely because a genetic cause is known. The existence of genetic and non-genetic causes must be considered when determining whether the relationship is appropriate.

#### Example:  Uroporphyrinogen decarboxylase deficiency

<table><thead><tr><th width="174.072998046875">Modeling component</th><th width="241.3697509765625">Etiologically unspecified concept</th><th>Genetic concept</th></tr></thead><tbody><tr><td>FSN</td><td>Deficiency of uroporphyrinogen decarboxylase (disorder)</td><td>Uroporphyrinogen decarboxylase gene-related uroporphyrinogen decarboxylase enzyme deficiency (disorder)</td></tr><tr><td>Genetic etiology</td><td>Not specified</td><td>Pathogenic variant in UROD</td></tr><tr><td>HAS ASSOCIATED GENE</td><td>Not asserted</td><td>Uroporphyrinogen decarboxylase gene (cell structure)</td></tr></tbody></table>

<br>


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://docs.snomed.org/snomed-ct-specifications/snomed-ct-editorial-guide/readme/authoring/domain-specific-modeling/clinical-finding-and-disorder/clinical-finding-and-disorder-modeling/specific-clinical-finding-and-disorder-modeling/enzyme-deficiency.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.