What is ICD-10 code D81.5?

D81.5 is the ICD-10-CM diagnosis code for Purine nucleoside phosphorylase [PNP] deficiency. A rare genetic disorder where the body lacks an enzyme called purine nucleoside phosphorylase, leading to a weakened immune system and neurological problems. D81.5 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. D81.5 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. D81.5 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. D81.5 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does D81.5 map to under V28?

D81.5 maps to CMS-HCC V28 HCC 114 (Common Variable and Combined Immunodeficiencies). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM D81.5: Purine nucleoside

D81.5 maps to CMS-HCC V28 114. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupD81.5

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (D50-D89) / Certain disorders involving the immune mechanism (D80-D89)

D81.5

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Purine nucleoside phosphorylase [PNP] deficiency

A rare genetic disorder where the body lacks an enzyme called purine nucleoside phosphorylase, leading to a weakened immune system and neurological problems.

Buddy Insight

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 114

Common Variable and Combined ...

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 073

HHS-HCC 073 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 47

Disorders of Immunity

Code-level coefficient reference

RXHCC

Mapped

HCC 99

Immune Disorders

Code-level coefficient reference

Code Book Path

Official

D81Combined immunodeficiencies D81.5Purine nucleoside phosphorylase [PNP] deficiency

Inclusion Terms

Official

No inclusion terms are included in this display for D81.5. Check the code and parent instructions in the Code Book.

Excludes 2

Official

autoimmune disease (systemic) NOS (M35.9)Inherited from D50-D89
certain conditions originating in the perinatal period (P00-P96)Inherited from D50-D89
complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from D50-D89
congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)Inherited from D50-D89
endocrine, nutritional and metabolic diseases (E00-E88)Inherited from D50-D89
human immunodeficiency virus [HIV] disease (B20)Inherited from D50-D89
injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from D50-D89
neoplasms (C00-D49)Inherited from D50-D89
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from D50-D89

Related Codes

Official

D81.0Severe combined immunodeficiency [SCID] with reticular dysgenesis D81.1Severe combined immunodeficiency [SCID] with low T- and B-cell numbers D81.2Severe combined immunodeficiency [SCID] with low or normal B-cell numbers D81.3Adenosine deaminase [ADA] deficiency D81.4Nezelof's syndrome

Includes

Official

defects in the complement systemInherited from D80-D89
immunodeficiency disorders, except human immunodeficiency virus [HIV] diseaseInherited from D80-D89
sarcoidosisInherited from D80-D89

Excludes 1

Official

autoimmune disease (systemic) NOS (M35.9)Inherited from D80-D89, D81
functional disorders of polymorphonuclear neutrophils (D71-)Inherited from D80-D89, D81
human immunodeficiency virus [HIV] disease (B20)Inherited from D80-D89, D81
autosomal recessive agammaglobulinemia (Swiss type) (D80.0)Inherited from D80-D89, D81

Code First

Official

No Code First sequencing instructions are included in this display for D81.5. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for D81.5. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for D81.5. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Documentation must include purine nucleoside phosphorylase enzyme activity levels, elevated uric acid levels (characteristically low in this condition despite being a purine disorder), lymphocyte subset analysis showing progressive T-cell decline, neurological assessment findings, and treatment plan.

Document any autoimmune manifestations and the distinction from adenosine deaminase deficiency.

MEAT Support

HCC Buddy guidance

Document any autoimmune manifestations and the distinction from adenosine deaminase deficiency.

Audit Caution

HCC Buddy guidance

Purine nucleoside phosphorylase deficiency characteristically causes LOW uric acid levels (unlike most purine disorders), which is an important diagnostic clue. Do not confuse with adenosine deaminase deficiency

the two affect different steps in purine metabolism and have distinct clinical profiles. Neurological manifestations should be coded separately (G80-G83 for spasticity, F70-F79 for intellectual disability).

Common Mistakes

HCC Buddy guidance

D81.31 (severe combined immunodeficiency due to adenosine deaminase deficiency, a different purine metabolism enzyme with different clinical features), D81.30 (adenosine deaminase deficiency, unspecified), D81.2 (severe combined immunodeficiency with low or normal B-cells from non-enzymatic causes), D81.89 (other combined immunodeficiencies without specified enzymatic defect).

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is D81.5 an HCC code?

Yes. D81.5 (Purine nucleoside phosphorylase [PNP] deficiency) maps to HCC 114, Common Variable and Combined Immunodeficiencies under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 2.262. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: D81.5 is billable and maps to V28 HCC 114, Common Variable and Combined Immunodeficiencies. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: D81.5
Description: Purine nucleoside phosphorylase [PNP] deficiency
HCC (V28): HCC 114 — Common Variable and Combined Immunodeficiencies
RAF reference coefficient: 2.262
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 114, Common Variable and Combined Immunodeficiencies

2.262

ESRDHCC 47, Disorders of Immunity

Not separately weighted

RxHCCHCC 99, Immune Disorders

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work D81.5 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for D81.5

For D81.5, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Coder workflow notes

Get the V28 mapping + MEAT cheat sheet

One printable reference: check representative V28 mappings and the documentation reminders your note needs. Free, no card.

Free PDF. No card. Unsubscribe anytime.

What This Code Means

D81.5 is the ICD-10-CM diagnosis code for purine nucleoside phosphorylase [pnp] deficiency. A rare genetic disorder where the body lacks an enzyme called purine nucleoside phosphorylase, leading to a weakened immune system and neurological problems. D81.5 sits in the ICD-10-CM chapter for diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (d50-d89), within the section covering certain disorders involving the immune mechanism (d80-d89).

Under the CMS-HCC V28 risk adjustment model, D81.5 maps to Common Variable and Combined Immunodeficiencies (HCC 114) with a source-labeled community, non-dual, aged reference coefficient of 2.262. No V24 mapping is shown for D81.5; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

This is a specific enzyme deficiency within combined immunodeficiency; do not use D81.9 if this specific deficiency is documented. For D81.5, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for D81.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This is a specific enzyme deficiency within combined immunodeficiency; do not use D81.9 if this specific deficiency is documented
•Often presents with severe infections, developmental delays, and autoimmune manifestations; document associated conditions separately

Clinical Significance

Purine nucleoside phosphorylase deficiency is a rare autosomal recessive immunodeficiency affecting purine metabolism, leading to progressive T-cell depletion due to accumulation of toxic deoxyguanosine triphosphate in lymphocytes. Uniquely, this condition also causes significant neurological manifestations including developmental delay, spasticity, and ataxia in approximately two-thirds of patients, distinguishing it from other combined immunodeficiencies.

Documentation Requirements

✓Documentation must include purine nucleoside phosphorylase enzyme activity levels, elevated uric acid levels (characteristically low in this condition despite being a purine disorder), lymphocyte subset analysis showing progressive T-cell decline, neurological assessment findings, and treatment plan.
✓Document any autoimmune manifestations and the distinction from adenosine deaminase deficiency.

Commonly Confused Codes

•D81.31 (severe combined immunodeficiency due to adenosine deaminase deficiency, a different purine metabolism enzyme with different clinical features), D81.30 (adenosine deaminase deficiency, unspecified), D81.2 (severe combined immunodeficiency with low or normal B-cells from non-enzymatic causes), D81.89 (other combined immunodeficiencies without specified enzymatic defect).