**1. Introduction**

Psoriatic arthritis (PsA) was first recognized as a specific rheumatic entity in 1964 by the American Rheumatism Association (later American College of Rheumatology) (Blumberg, 1964). In the forthcoming years it has become clear that PsA belongs to the spondyloarthritis (SpA) family that comprises several heterogeneous clinical conditions. These are Ankylosing Spondylitis, Reactive Arthritis (which occurs after bacterial infections), Spondyloarthritis associated to Chronic Inflammatory Bowel Diseases (Crohn´s disease and Ulcerative Colitis), Undifferentiated Spondyloarthritis, and juvenile forms (figure 1). The term spondyloarthritis relates to inflammatory manifestations of peripheral and spinal joint structures. The Spondyloarthitides are defined by classification criteria (Sieper, 2009; Zeidler 2011, Rudwaleit 2011). The main clinical manifestation will trigger the main group for each disease entity may have varying degrees of articular, spinal, and extraaticular manifestations. Furthermore, extraarticular inflammatory manifestations may also occur at different intensity levels. However, it needs to emphasized that classification criteria are not diagnostic criteria. Classification criteria were developed for clinical studies in order to include rather homogenous disease manifestations. In daily clinical practice it may occur that although the classification criteria are not fully met, the patient still may be allocated to a certain disease entity.


Table 1. Clinical manifestation of the Spondyloarthritides, which may be present in all the different disease entities (Fig. 1).

Detecting Psoriasis Arthritis Early in the Disease Course – Why This

actual joint destruction can be seen on conventional X-ray films.

rheumatologists can be effectively set up will be given at the end.

**2.1 The earlier the better or time is joint function** 

more or less destruction of joint structures.

Beginn of Psoriasis Arthritis

to (Machold, 1998).

**Remitting arthritic inflammation** 

**2. Why is early detection of inflammatory processes important?** 

textbooks.

is Important and How Dermatologists and Rheumatologists Can Successfully Cooperate? 67

diagnostics of the sacroiliac joints (Rudwaleit, 2009). Bone marrow edema around the sacroiliac joints seen in MRI in water sensitive squences, i.e. STIR (short tau inversion recovery, T1 plus contrast media) detects inflammatory processes significantly earlier than

However, we still do not have validated early PsA criteria and early PsA most times does not present with the classical, fully developed clinical picture as is described in our

This book chapter is dedicated to discuss why we need to detect PsA early and will answer the question of how patients with psoriasis can be screened for possible early peripheral and spinal arthritis manifestations. Suggestions on how cooperation between dermatologists and

Early detection and treatment of chronic inflammatory joint disease has been shown in numerous reports to correlate with better long-term outcome in rheumatoid arthritis (van der Bijl, 2007; Verstappen, 2007). Severity of joint destruction and loss of quality of life in PsA has been shown to be similar to RA (Husted, 2001; Rahman, 2001). Therefore, many aspects in PsA may be compared with aspects in RA. As depicted in figure 2, the chronic inflammatory process begins with an undulating situation of clinical and subclinical manifestations of joint pain with or without swelling. A trigger event then sets off the clinical manifest chronic inflammatory course. Joint destruction begins very early after this event. If the inflammatory process is not stopped, the natural disease course will occur with

Fig. 2. Time course of the development of PsA. The earlier detection and treatment of

**joint destruction** 

arthritis takes place, the better the outcome in the following years will be, adapted according

**time Beginn of** 

**Idealy, very early induced therapy** 

**Natural** **disease**

**Early induced therapy** 

**course**

**Late induced therapy** 

**Degree of destruction in PsA** 

Fig. 1. Clinical entities of Spondyloarthritis. The overall disease group is the Spondyloarthritis, which comprises 6 distinct diseases. Psoriasis Arthritis is one disease entity of the group. Common abbreviations are given in parenthesis.

In clinical practice, articular and extraarticular manifestations overlap quite frequently among the SpA diseases. Initially, the clinical manifestations of PsA were collected and a set of manifestations was proposed as classification criteria by Moll and Wright in 1973 (Moll, 1973). These described clinical features were considered to be "Psoriatic Arthritis". However, over the following years, 6 modified classification criteria for PsA (Bennet, 1979; Dougados, 1991; Fournie, 1999; Gladman, 1987; McGonagle, 1999; Vasey, 1984) have been proposed by different research groups in order to differentiate between the different disease entities (Taylor, 2002). As in the Moll and Wright criteria proposal, these criteria mainly have been established in groups of patients with classical and fully developed disease manifestations. The validity of these criteria have never been formally proven in studies. Formal prove of PsA criteria was done in 2006 with the publication of the CASPAR (Classification of Psoriasis Arthritis Study Group)-Criteria (Taylor, 2006) as a joint project of the EUAR and ACR. As with the other above mentioned 7 criteria sets, the CASPAR criteria also were established in a group of patients with long standing psoriasis arthritis (mean disease duration of greater than 10 years (Taylor, 2006). As we know that chronic inflammatory arthritis like Rheumatoid Arthritis (RA) and PsA can destroy joints and cause significant disability (see Tab. 1) we need to diagnose arthritis before destruction of tissue has taken place. For this reason, in RA, arthritis classification criteria have just been revised to also classify early RA (Aletaha, 2010). Next to the new RA early classification criteria, the newly proposed classification criteria for spinal spondyloarthritis now include MRI diagnostics of the sacroiliac joints (Rudwaleit, 2009). Bone marrow edema around the sacroiliac joints seen in MRI in water sensitive squences, i.e. STIR (short tau inversion recovery, T1 plus contrast media) detects inflammatory processes significantly earlier than actual joint destruction can be seen on conventional X-ray films.

However, we still do not have validated early PsA criteria and early PsA most times does not present with the classical, fully developed clinical picture as is described in our textbooks.

This book chapter is dedicated to discuss why we need to detect PsA early and will answer the question of how patients with psoriasis can be screened for possible early peripheral and spinal arthritis manifestations. Suggestions on how cooperation between dermatologists and rheumatologists can be effectively set up will be given at the end.
