Quick answer
Psoriasis is coded in ICD-10-CM category L40, with the code chosen by the type of psoriasis the provider documents (for example L40.0 for plaque psoriasis vulgaris or L40.4 for guttate psoriasis). Psoriatic arthritis is coded in the L40.5- subcategory. Treatments such as phototherapy, excimer laser and biologic injections are reported with their own CPT and HCPCS codes, linked to the L40 diagnosis.
What Is Psoriasis?
Psoriasis is a chronic, immune-mediated skin disease that speeds up skin cell turnover, producing thick, scaly, red or silvery plaques. It commonly affects the scalp, elbows, knees, lower back, nails and skin folds, and it can be associated with itching, pain and joint disease. Because psoriasis is chronic and often treated with phototherapy or expensive biologic drugs, accurate coding is essential for reimbursement, prior authorization and medical necessity.
ICD-10-CM Codes for Psoriasis (FY2027)
Psoriasis codes are in category L40 in Chapter 12 (Diseases of the Skin and Subcutaneous Tissue).
| Code | Description |
| L40.0 | Psoriasis vulgaris (plaque psoriasis) |
| L40.1 | Generalized pustular psoriasis |
| L40.2 | Acrodermatitis continua |
| L40.3 | Pustulosis palmaris et plantaris |
| L40.4 | Guttate psoriasis |
| L40.50 | Arthropathic psoriasis, unspecified |
| L40.51 | Distal interphalangeal psoriatic arthropathy |
| L40.52 | Psoriatic arthritis mutilans |
| L40.53 | Psoriatic spondylitis |
| L40.54 | Psoriatic juvenile arthropathy |
| L40.59 | Other psoriatic arthropathy |
| L40.8 | Other psoriasis (for example, inverse or flexural psoriasis) |
| L40.9 | Psoriasis, unspecified |
Always code to the highest level of specificity the provider documents. L40.5 is a subcategory heading and cannot be reported by itself.
Key Coding Guidelines for Psoriasis
Read the documentation for type and joint involvement
The type of psoriasis drives the code. Look for terms such as plaque, vulgaris, guttate, pustular, palmoplantar, inverse or erythrodermic, and for any mention of joint pain, dactylitis, enthesitis or a psoriatic arthritis diagnosis.
Code psoriatic arthritis in L40.5-
Psoriatic arthritis is reported with the L40.5- codes, which capture both the skin disease and the joint disease in one code. Do not add a separate arthritis code for the same condition. If the provider documents psoriatic arthritis without saying which form, use L40.50.
Severity and body surface area support medical necessity
ICD-10-CM does not have separate codes for mild, moderate or severe psoriasis, but payers rely on documented severity, the percentage of body surface area (BSA) involved, scores such as PASI and prior treatment failures to approve phototherapy and biologics. Make sure these details are in the note when those services are billed.
Report long-term drug therapy when documented
When a patient is on ongoing immunosuppressive treatment, add the appropriate Z79 long-term drug therapy code, such as Z79.620 for long term (current) use of an immunosuppressive biologic. See our guide to long-term drug therapy codes in ICD-10-CM.
Avoid unspecified codes
Use L40.9 only when the documentation truly does not identify the type. Learn more in our post on unlisted and unspecified codes.
CPT and HCPCS Codes for Psoriasis Treatment
| Service | Code(s) |
| Office or outpatient E/M visit | 99202 to 99215 |
| Actinotherapy (ultraviolet light) | 96900 |
| Photochemotherapy: tar and UVB (Goeckerman) or petrolatum and UVB | 96910 |
| Photochemotherapy: psoralens and UVA (PUVA) | 96912 |
| Photochemotherapy for severe photoresponsive dermatoses requiring at least 4 to 8 hours of care under direct physician supervision | 96913 |
| Excimer laser treatment for psoriasis, by total area treated | 96920 (under 250 sq cm), 96921 (250 to 500 sq cm), 96922 (over 500 sq cm) |
| Therapeutic injection, subcutaneous or intramuscular | 96372 |
| Biologic drug supplied in the office | The drug’s HCPCS J or Q code, with the NDC when the payer requires it |
Many biologics are self-administered at home and billed through pharmacy benefits rather than on the medical claim. For office-administered drugs, see our guide to HCPCS drug coding and the National Drug Code (NDC).
Psoriasis Coding Example
Scenario: An established patient returns for plaque psoriasis covering about 12% body surface area on the trunk and extremities, with new swelling and pain in the distal finger joints. The dermatologist documents psoriasis vulgaris with distal interphalangeal psoriatic arthropathy and continues the patient’s injectable biologic, administered subcutaneously in the office.
- ICD-10-CM: L40.51 Distal interphalangeal psoriatic arthropathy, plus Z79.620 for the ongoing biologic.
- CPT/HCPCS: the documented E/M level, 96372 for the injection, and the HCPCS code for the biologic.
Because L40.51 already captures psoriasis with joint involvement, L40.0 is not reported separately for the same skin disease.
Common Psoriasis Coding Mistakes
- Reporting L40.9 when the note clearly says plaque, guttate or pustular psoriasis
- Missing psoriatic arthritis that is documented in the assessment
- Reporting the subcategory heading L40.5 instead of a complete code
- Choosing the wrong phototherapy code, for example using 96912 (PUVA) for UVB treatment
- Billing biologics or phototherapy without documented severity, BSA or prior treatment history
Frequently Asked Questions About Psoriasis Coding
What is the ICD-10 code for plaque psoriasis?
Plaque psoriasis is psoriasis vulgaris, L40.0.
What is the ICD-10 code for psoriatic arthritis?
Psoriatic arthritis is coded in L40.5-. Use the specific form documented, or L40.50 when the type of arthropathy is not specified.
Is there an ICD-10 code for scalp psoriasis?
There is no separate scalp code. Code the type of psoriasis documented, most often L40.0 for plaque psoriasis of the scalp.
Does ICD-10-CM capture psoriasis severity?
No. Severity and body surface area are documented in the note to support medical necessity, but they do not change the L40 code.
What CPT code is used for narrowband UVB phototherapy?
UV light therapy without a photosensitizing agent is reported with 96900. Code 96910 is for UVB combined with tar or petrolatum, and 96912 is for PUVA. Check payer policy, since some payers have specific rules for narrowband UVB.
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