The nail involvement and prolonged nail bed psoriasis were common in PsA patients. Nail fold psoriasis and DIP joint arthritis were associated with nail involvement in PsA patients. Nail psoriasis would be related to the Koebner phenomenon and local inflammatory DIP joint arthritis in PsA patients, and we suggested that nail involvement in PsA was among the disorders indicative of distal phalanx enthesitis.

To identify diagnostic markers for psoriasis vulgaris and psoriatic arthritis, autoantibodies in sera from psoriasis vulgaris and psoriatic arthritis patients were screened by two-dimensional immunoblotting (2D-IB). Based on 2D-IB and MADLI TOF/TOF-MS analyses, eleven proteins each in psoriasis vulgaris and psoriatic arthritis were identified as autoantigens. Furthermore, serum levels of moesin, keratin 17 (K17), annexin A1 (ANXA1), and stress-induced phophoprotein-1 (STIP1), which were detected as autoantigens, were studied by dot blot analysis with psoriasis patients and healthy controls. The levels of moesin and STIP1 were significantly higher in sera from patients with psoriasis vulgaris than in the controls (moesin: P<0.05, STIP1: P<0.005). The area under the curve (AUC) for moesin and STIP1 between patients with psoraisis vulgaris and controls was 0.747 and 0.792, respectively. STIP1 and K17 levels were significantly higher in sera from patients with psoriatic arthritis than in those with psoriasis vulgaris (P<0.05 each). The AUC for STIP1 and K17 between patients with psoriatic arthritis and psoriasis vulgaris was 0.69 and 0.72, respectively. The STIP1 or moesin, CK17 serum level was not correlated with disease activity of psoriasis patients. These data suggest that STIP1 and moesin may be novel and differential sero-diagnostic markers for psoriasis vulgaris and psoriatic arthritis.

The early psoriatic arthritis screening questionnaire (EARP) is a simple and fast method for the identification of arthritis in patients with psoriasis. We established the Japanese version of the EARP (J-EARP) questionnaire, which includes 10 items with two choices for each. This study aimed to evaluate the utility of the J-EARP questionnaire. A total of 90 psoriasis patients, 19 psoriatic arthritis (PsA) patients and 71 psoriasis patients without joint involvement, were administered the J-EARP questionnaire. The diagnostic accuracy of the J-EARP questionnaire for the diagnosis of PsA and early-stage PsA was compared by receiver-operator curve (ROC) analysis. The J-EARP questionnaire showed similar ROC characteristics to those of the original version of the EARP (specificity 97.2% and 91.6% and sensitivity 97.2% and 85.2%, respectively) in PsA patients using the cut-off value of 3 for the J-EARP questionnaire, which was the same as that used for the original EARP questionnaire. The scores of the J-EARP questionnaire in early-stage PsA patients (<1 year from onset) were significantly higher than in those of psoriasis patients, but not lower than in those of later stage (≥1 year from onset) PsA patients. The J-EARP questionnaire is simple and fast to administer and has been proven to be robust for the identification of PsA. The J-EARP questionnaire is a useful diagnostic tool for early-stage PsA patients.

A neutral cysteine protease, bleomycin hydrolase (BH), is widely expressed in mammalian tissues, with the skin seeming to contain the highest level. Our previous study revealed that BH transcription is modulated both during differentiation and by cytokines. However, BH involvement in keratinization disorder is not well known. In the present study, we performed immunohistochemical studies of BH and other serine/cysteine proteases in human normal skin and lesional skin with keratinization disorders. BH-positive cells were detected in granular layers of orthokeratotic and hyperkeratotic skin diseases, such as erythrokeratoderma and lichen planus. In parakeratotic skin diseases with porokeratosis, pityriasis rubra pilaris and psoriasis, BH staining was decreased in lesional skins compared to that in normal skin. Similar results were obtained for cysteine proteases, caspase-14 and calpain I. On the other hand, cells positive for serine proteases kallikrein 5 and 7 were increased in parakeratotic and inflammatory skin diseases, such as psoriasis. Semi-quantification analysis revealed that BH- and caspase-14-positive staining had higher intensity than those of the other proteases in normal epidermis. As BH is the major citrulline aminopeptidase in normal granular layer, the alternation would have a significant effect on terminal differentiation processes, such as aberrant processing of deiminated peptides. Therefore, BH may play an important role during the late stage of epidermal differentiation.

Anti-cyclic citrullinated peptide antibodies (anti-CCP) are highly considered to indicate disease severity and be predictive markers in rheumatoid arthritis (RA). RA patients who are positive for anti-CCP tend to progress more frequently to joint deformity and functionally deteriorate more than negative patients. A study concerning the presence of anti-CCP in Japanese patients with psoriatic arthritis (PsA) has been published. Our aim was to clarify that anti-CCP could be a potentially useful marker in PsA patients. We herein describe a PsA patient with presence of anti-CCP. We examined anti-CCP in 15 patients with PsA, and compared with 18 controls who had other types of psoriasis. Three PsA patients were positive for anti-CCP, but no controls showed positive. The anti-CCP-positive patients had higher counts of radiographic erosion, higher prevalence rates of polyarticular disease, use of disease-modifying anti-rheumatic drugs, and the human leukocyte antigen DRB1*04 shared epitope than negative patients. Our study demonstrated that anti-CCP was potentially both predictive and a severity marker of joint involvement in PsA, the same as in RA.