2027 ICD-10-CM Diagnosis Code E79.1Lesch-Nyhan syndrome
ICD-10-CM Codes›E00–E89›E70-E88›E79
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 50
- Chronic Condition
E79.1 is a billable ICD-10-CM diagnosis code for Lesch-Nyhan syndrome. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 642. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 35 closely related codes. Coders also document this condition as blood urate above reference range. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified nutritional and metabolic disorders.
For Medicare Advantage risk adjustment, E79.1 maps to CMS-HCC Category 50 (Amyloidosis, Porphyria, and Other Specified Metabolic Disorders) under the V28 model, adding a risk factor of about 0.648 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
E79.1 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Blood urate above reference range
- Chorea due to Lesch-Nyhan syndrome
- Chorea due to metabolic disorder
- Deficiency of hypoxanthine phosphoribosyltransferase
- Dystonia due to Lesch Nyhan syndrome
- Hyperuricemia
- Lesch-Nyhan syndrome
- Partial hypoxanthine-guanine phosphoribosyltransferase deficiency
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to E79.1: its own notes plus those printed at E79, block E70-E88, and Chapter 4. A note printed at a category, block or chapter applies to every code under it.
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- HGPRT deficiency
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- Ehlers-Danlos syndromes (Q79.6-)
Notes
General instructions on how these codes are used.
- All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere.
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name E79.1, its category, or a range that includes it.
Excludes1 2
These codes carry an Excludes1 note naming E79.1: they are not reported together with it, unless the two conditions are unrelated.
Excludes2 1
These codes carry an Excludes2 note naming E79.1: its condition is not part of those codes, and both may be reported when the patient has both.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Arthropathy See Also: Arthritis; M12.9
gouty See Also: Gout;
Lesch-Nyhan syndrome E79.1
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Lesch-Nyhan Syndrome
an inherited disorder transmitted as a sex-linked trait and caused by a deficiency of an enzyme of purine metabolism; hypoxanthine phosphoribosyltransferase. affected individuals are normal in the first year of life and then develop psychomotor retardation, extrapyramidal movement disorders, progressive spasticity, and seizures. self-destructive behaviors such as biting of fingers and lips are seen frequently. intellectual impairment may also occur but is typically not severe. elevation of uric acid in the serum leads to the development of renal calculi and gouty arthritis. (menkes, textbook of child neurology, 5th ed, pp127)
Patient EducationClinical
Amino Acid Metabolism Disorders
Metabolism is the process your body uses to make energy from the food you eat. Food is made up of proteins, carbohydrates, and fats. Your digestive system breaks the food parts down into sugars and acids, your body's fuel. Your body can use this fuel right away, or it can store the energy in your body.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert E79.1 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About E79.1Overview
What is the ICD-10 code for Lesch-Nyhan syndrome?
The ICD-10-CM code for Lesch-Nyhan syndrome is E79.1 (sometimes written as E791). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is E79.1 (Disorders of purine and pyrimidine metabolism) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report Lesch-Nyhan syndrome on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does E79.1 group to?
When Lesch-Nyhan syndrome is the principal diagnosis on an inpatient stay, it groups to MS-DRG 642 (inborn and Other Disorders of Metabolism), which carries a relative weight of 1.3226. Higher weights mean higher Medicare reimbursement.
Is E79.1 a CC or MCC?
CMS lists E79.1 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 35 closely related codes in its exclusion list.
Can E79.1 be reported with Q87.19?
Not as a rule. The Excludes1 note at E79, which applies to E79.1, lists "Ataxia-telangiectasia (Q87.19)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What HCC is E79.1?
E79.1 (Lesch-Nyhan syndrome) maps to CMS-HCC Category 50 (Amyloidosis, Porphyria, and Other Specified Metabolic Disorders), commonly written as HCC 50, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 23 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 43.
Does E79.1 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, E79.1 adds a risk adjustment factor of about 0.648 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.362 to 0.883 depending on the payment segment). HCC 50 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 50 category page.
