Set the Record Straight About Psoriatic Arthritis

Set the Record Straight About Psoriatic Arthritis

Get a clear picture of what it is to help you report an accurate diagnosis code.

By Anissa Calhoun, COC, CPC, CDEO, AAPC Fellow
Many people are unsure of what psoriatic arthritis (PsA) is, or mistakenly think it is rheumatoid arthritis (RA). PsA is similar to RA, but confusing the two will lead to incorrect coding. Take a moment to learn their differences and better understand PsA etiology, treatment, and diagnosis coding.

RA vs. PsA

RA typically affects joints symmetrically and affects the lining of the joints, eventually causing bone erosion and joint deformity. PsA is an autoimmune, inflammatory disorder that occurs in approximately 15-30 percent of people with psoriasis, and can occur in people without the skin symptoms of psoriasis. Unlike RA, PsA can affect any joint in any pattern, and may affect one joint at a time, to start. It typically affects the distal joints in the fingers and toes, but can also affect other joints, including the spine (spondylitis), sacroiliac joint, knees, wrists, elbows, and ankles.

Signs and Symptoms of PsA

The typical symptoms of PsA can include:

  • Tender, swollen, and painful joints;
  • “Sausage digits” (dactylitis-inflammation/swelling of an entire finger or toe, giving it the appearance of a sausage link);
  • Fatigue;
  • Nail changes (pitting, white patches);
  • Reduced range of motion of affected joints; and
  • Tenderness, pain, and swelling of the areas where tendons and ligaments join onto bones (enthesitis).

Enthesitis and dactylitis are two characteristic features of PsA not found together in any other form of arthritis. Symptoms can vary and can range from mild to severe, and may present occasionally or continuously.
Patients with PsA are also at risk of developing certain complications. One of the most damaging is arthritis mutilans, which destroys the small bones in the hands — especially the distal interphalangeal and proximal interphalangeal joints due to osteolysis, which causes permanent deformity. The patient also may experience eye problems such as conjunctivitis, uveitis, and an increased risk of cataracts and glaucoma.
Patients with PsA are also more likely to develop comorbid conditions, including stroke, cardiovascular problems, depression, Crohn’s disease, metabolic syndrome, diabetes mellitus type 2, lymphoma, skin cancer, obesity, osteoporosis (especially in men), nonalcoholic fatty liver disease, and hearing loss.

PsA Treatment

Regular appointments with a primary care physician, ophthalmologist, and rheumatologist are critical to keep symptoms, complications, and risk of comorbid conditions at a minimum. Available treatments include:

  • Non-steroidal anti-inflammatory drugs (such as Mobic, Naprosyn, Relafen, and Voltaren);
  • Disease-modifying antirheumatic drugs (DMARDs) (such as Methotrexate);
  • Biologics that affect the immune system, either by blocking T-cells or certain proteins known as interleukins 17-A, 12 and 23 or TNF-alpha (such as Enbrel, Humira, Remicade, Simponi, Cimzia, Stelara, Orencia, Taltz, Siliq, Tremfyz, and Cosentyx); and
  • Newer medications on the market (such as Otezla).

Some of these medications require periodic bloodwork during treatment and others require bloodwork, a TB test, and Hepatitis B and C tests before starting treatment. As with all medications, there can be side effects, such as stomach irritation, heart problems, liver damage, bone marrow suppression, severe lung infections, and being more susceptible to other infections.

Diagnosis Coding

Etiology and treatment can be helpful when reviewing charts for documentation improvement, especially with the new quality payment models. ICD-10 codes for psoriasis are in the range of L40.0-L40.9, with the PsA codes in the range of L40.50-L40.59.
Diagnosis codes include:
L40 Psoriasis
L40.0 Psoriasis vulgaris

Nummular psoriasis

Plaque psoriasis

L40.1 Generalized pustular psoriasis

Impetigo herpetiformis

Von Zumbusch’s disease

L40.2 Acrodermatitis continua
L40.3 Pustulosis palmaris et plantaris
L40.4 Guttate psoriasis
L40.5 Arthropathic 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

Flexural psoriasis

L40.9 Psoriasis, unspecified

Case 1 

Assessment and Plan:
This 46-year-old female with PsA comes in with new onset of right knee pain, bilateral elbow pain, bilateral foot pain, L index finger pain, and full finger swelling after a 5-year period of remission. The patient had previously used methotrexate for 1.5 years, and has been off all meds in the interim.
We will check CRP, CBC, CMP.
We will check hep and TB serologies.
We will start methotrexate at 17.5 mg a week, and folic acid 1 mg a day, as she has had worsening polyarticular joint pain.
We will see in 2 months.
Diagnosis: Psoriasis with arthropathy, L40.50.

Case 2 

Reason for visit: The patient returns today for evaluation of her various left foot problems. The patient still has edema in the left foot, most notably in the second toe, as well as both hands. Patient still has MP joint pain with motion, and motion is restricted. Patient is now having discomfort in her knees and one of the MCP joints in the right hand.
Labs from last visit:
CRP 44.8 mg/L High, range 0.0-4.9 mg/L
Sedimentation rate-Westergren 66 mm/hr High, range 0-20 mm/hr
Assessment and Plan:
Because of the multiple joint involvement, I elected to do general arthritic profile labs at the last visit, which was remarkable for elevated CRP and sed rate. Based on this, I am referring patient to a rheumatologist with a current diagnosis of metabolic inflammatory disorder, not yet diagnosed.
This patient was later diagnosed with psoriatic arthritis by the rheumatologist, L40.50.

Mayo Clinic:
National Psoriasis Foundation:
American College of Rheumatology:
Anissa Calhoun, COC, CPC, CDEO, AAPC Fellow, began her diverse healthcare experience more than 15 years ago working as a medical assistant, pharmacy technician, insurance specialist, and then office manager. She then began her coding career in 2007, was certified in 2009, and now works as a coding specialist for Partners Healthcare in Boston. Calhoun is a member of the Chapel Hill, N.C., local chapter.

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