by Don R. Martin, M.D.
- History of Present Illness
- Presentation to the Johns Hopkins Rheumatology Clinic
- Physical Examination
- Differential Diagnosis
- Additional Diagnostic Studies
- Subsequent Course
- Summary of Teaching Points
The patient is a 40-year-old Hispanic gentleman and is a dedicated long distance runner. He had a 1-year history of right ankle arthralgias and a 2-month history of right knee arthralgias. Then, during a meeting he was attending in the U.S., he developed right thigh, calf & foot swelling, and a right knee effusion.
Evaluation yielded the following:
- Laboratory findings
– ESR 40 mm/hr
– normal CBC, differential & uric acid
- Right leg venous Doppler – negative for DVT
- Right knee MRI – positive for a ruptured Bakers cyst
Subsequent evaluation included:
- Orthopedics consultation x 4
- Rheumatology consultation x 1
- Emergency Department evaluation x 1
These evaluations revealed the following:
- Laboratory findings – normal comprehensive metabolic profile, ESR, urinalysis, and Lyme ELISA & Western blot
- Arthrocentesis x 3 (representative values):
- WBC – 10,683/mm3
- Differential – 79% neutrophils and 21% mononuclear cells
- Crystals – none
- Bacterial culture – negative
- Right leg venous Doppler – positive for a Bakers cyst
- Abdomino-pelvic CT scan – normal
- Celecoxib, indomethacin & nabumetone
- Intra-articular corticosteroids
He had persistent right leg swelling but the effusion in his right knee had resolved. He had a new effusion in his left knee and had developed arthalgias in the left ankle.
- Past Medical History, Family History & Social History – unremarkable
- Review of Systems:
- Rash or psoriasis – none
- Ocular inflammation – none
- Cough or dyspnea – none
- Cramping, diarrhea, hematochezia or mucous stool – none
- Dysuria or genital lesions – none
- Low back pain – present
- Low back stiffness – none
- Tick exposure – none
- Right 4th and 5th fingernails – isolated “pitting”
- Psoriatic plaques – none
- Oral mucosa – no lesions
- Eyes – no inflammation
- Chest – clear
- Abdomen – benign
- Stool Hemoccult – positive
- Peripheral articular:
- Right knee synovitis – none
- Left knee synovitis – present
- Left ankle synovitis – none
- Axial articular:
- Sacro-iliac joint tenderness – none
- Schober test – 4 cm lumbar distraction
- [ ] Trauma
- [ ] Microcrystalline arthritis
- [ ] Septic/viral arthritis
- [ ] Lyme disease
- [ ] Rheumatoid arthritis
- [ ] Sarcoidosis
- [ ] Sero-negative spondyloarthropathy
- CBC & differential – normal
- Rheumatoid factor – negative
- Lyme serology – negative
- Parvovirus serology – negative
- Chest x-ray – normal
- Sacro-iliac joint x-ray – normal
- This narrowed the differential diagnosis to a sero-negative spondyloarthropathy. Possiblities included:
- Ankylosing spondylitis
- Inflammatory bowel disease
- Psoriatic arthritis
- Reiters syndrome
- Further evaluation revealed:
- History – “Dandruff” x 3 months
–Scaling plaque right occiput
-Dactylitis right 3rd toe
- EGD & colonoscopy with biopsy – normal
- Dermatology consult with biopsy – Psoriasis
These pharmacologic interventions were initiated sequentially, in combination with physical therapy:
- Intra-articular corticosteroid injection
- Methotrexate (7.5 mg-15 mg weekly) x 5 months
- Etanercept (25 mg SQ b.i.w.)
He had a dramatic clinical response in all respects except for persistent and diffuse right leg swelling.
Five percent of patients with psoriasis are affected by an inflammatory arthritis in some form. Men and women are affected with equal frequency. Psoriatic skin disease may pre-date the onset of arthritis (70% of cases), present coincident with arthritis (15% of cases), or follow the onset of arthritis (15% of cases).
Characteristic, but not necessarily pathognomonic, features of psoriatic arthritis include nail involvement (pitting, separation from the nail bed known as “onycholysis”, and yellow discoloration known as the “oil drop” sign); dactylitis (“sausage digits”); inflammation at the sites of ligamentous and tendonous insertion (“enthesopathy”); and absence of rheumatoid factor.
There are five clinical patterns of psoriatic arthritis, which may evolve and are not necessarily mutually exclusive:
- Symmetrical polyarticular (30-50% of cases)
- Asymmetrical oligoarticular (30-50% of cases)
- Distal interphalangeal joint involvement (25% of cases)
- Arthritis mutilans (characterized by resorption of the phalangeal bones) (5% of cases)
- Axial arthritis (includes both sacro-iliitis which may be asymmetric & spondylitis)
Extra-articular manifestations are uncommon but may include uveitis, aortic insufficiency, and pulmonary fibrosis.
Radiographically, psoriatic arthritis is a unique blend of bone destruction & proliferation. Manifestations may include erosive arthritis giving rise to the classic “pencil-in-cup” deformity in the phalanges, osteolysis, sacro-iliitis, ankylosis, spondylitis, enthesopathy, and periostitis.
Our understanding of the etiology and pathophysiology of psoriatic arthritis remains incomplete. However, what is known can be summarized as follows. Genetic factors play an important role as evidenced by the 70% concordance for psoriasis in monozygotic twins; 50-fold increased risk of developing psoriatic arthritis in 1st degree relatives of patients with the disease; and epidemiologic association with the expression of both class I and class II HLA alleles including -B13, -B17, -B27, -B38, -B39, -Cw6, -DR4, and -DR7. Environmental factors have also been implicated including infectious agents (streptococci & staphylococci) and trauma (“Koebner phenomenon”) that may precipitate the onset or a flare of disease activity. T-cells have been demonstrated to play a role in both initiation and perpetuation of disease activity. Interestingly, peripheral joint activity in psoriatic arthritis parallels cutaneous activity in 1/3 of cases.
Treatment options include NSAIDs, intra-articular or low-dose systemic corticosteroids, and a variety of “disease-modifying” agents including anti-malarials, gold, methotrexate, sulfasalazine, azathioprine, and cyclosporin A. The TNF inhibitor, etanercept (Enbrel®) is also an approved therapy for patients with psoriatic arthritis.
Factors which portend a worse prognosis include a strong family history of psoriasis, disease onset <20 years of age, expression of HLA-B27 or -DR4 alleles, polyarticular disease, erosive disease, and extensive skin involvement.
- The cutaneous manifestations of psoriatic arthritis may be scant or non-existent and need to be looked for carefully on examination.
- Nail pitting and dactylitis, while not specific, are highly suggestive of psoriatic arthritis.
- The patterns of joint involvement in psoriatic arthritis are variable.
Boumpas D, Tassiulas I. Psoriatic Arthritis. Primer on the Rheumatic Diseases. Klippel J (ed). Arthritis Foundation, 1997.
Gladman D, Rahman P. Psoriatic Arthritis. Kelley’s Textbook of Rheumatology. W.B. Saunders, 2001.