Psoriatic arthritis: Epidemiology, diagnosis, and treatment

Table 1 The classification for psoriatic arthritis criteria[7] for diagnosing psoriatic arthritis-related inflammatory musculoskeletal disease (joint, spine or entheseal)

Evidence of psoriasis (any of three)

Current1: Psoriatic skin or scalp disease present, as judged by a dermatologist or rheumatologist (score of 2)

Personal history: May be obtained from the patient, family doctor, dermatologist, or rheumatologist (score of 1)

Family history: In a first- or second-degree relative, according to patient report (score of 1)

Psoriatic nail dystrophy

Typical psoriatic Nail dystrophy, including onycholysis, pitting, and hyperkeratosis, observed on current physical examination (score of 1)

Negative rheumatoid factor

By any method except latex, but preferably by enzyme-linked immunosorbent assay or nephelometry, according to the local laboratory reference range (score of 1)

Dactylitis

Current: swelling of an entire digit (score of 1)

Personal history: recorded by a rheumatologist (score of 1)

Radiological evidence of juxta-articular new bone formation

Ill-defined ossification near the joint margins (but excluding osteophyte formation) on plain X-rays of the hand or foot (score of 1)

¹Current: Psoriasis score of 2; others: 1. A PsA patient must have inflammatory articular disease with > 3 points from the following 5 categories.

Table 2 Comparison of the incidence and prevalence of psoriatic arthritis among several countries

Country	Incidence (1/100000)	Ref.	Prevalence	Ref.
Asia
China	NA		0.02%	[33]
Japan	0.1	[17]	0.001%	[32]
Europe	NA		NA
Greece	3	[20]	0.17%	[29]
France	NA		0.19%	[23]
Italy	NA		0.42%	[25]
Germany	NA		0.29%	[24]
Finland	23.1	[18]	NA
Sweden	8	[19]	0.02%-0.25%	[30]
Iceland	NA		0.14%	[28]
Norway	NA		0.2%	[27]
Russia	NA		0.3%	[31]
Americas
United States	7.2	[22]	0.16%	[22]
Argentina	6.3	[92]	0.07%	[21]
Mexico	NA		0.02%	[26]

NA: Not available.

Table 3 Summary of current biologic therapies for the treatment of psoriasis and psoriatic arthritis[63-65]

Drug	Treatment
Anti-TNF
Adalimumab	PsA: 40 mg sc every other week. Psoriasis: 80 mg sc at week 0, 40 mg sc every other week thereafter
Etanercept	PsA: 25 mg sc twice per week. Psoriasis: 50 mg sc twice weekly for 3 mo, 50 mg/wk thereafter
Golimumab	PsA: 50 mg sc every month
Infliximab	PsA and psoriasis: 5 mg/kg at week 0, 2, and 6, every 8 wk thereafter
Anti-IL-17
Brodalumab	In clinical trials
Ixekizumab	In clinical trials
Secukinumab	In clinical trials
Anti-IL-12/IL-23
Briakinumab	In clinical trials
Ustekinumab	Psoriasis: 45 mg (weight < 100 kg) or 90 mg (weight > 100 kg) sc at wk 0 and 4, followed by 45 mg or 90 mg every 12 wk
Anti-T cell activation
Alefacept	Psoriasis: 15 mg IM weekly for 12 wk

PsA: Psoriatic arthritis; SC: Subcutaneous injection; IM: Intramuscular injection; TNF: Tumor necrosis factor; IL: Interleukin.