Background/Purpose: Patients with Psoriatic arthritis (PsA) who develop severe joint damage have severe functional disability and increased mortality risk. The most severe form of PsA is termed arthritis mutilans and is associated with severe erosions, osteolysis and pencil-in-cup change. Ankylosis is also a feature of severe PsA. The modified Steinbrocker method of scoring radiographic damage to peripheral joints in PsA recognizes grade 4 damage as severe damage, but does not explicitly distinguish between severe erosions, pencil-in-cup change, subluxation and ankylosis. We aimed to describe the prevalence and disease association of these features of severe joint damage in a cohort of patients with early PsA.

Methods: Patients presenting to a large PsA clinic with PsA duration of < 5years were identified. Patients are evaluated every 6-12 months and plain radiographs are obtained every 2 years. Radiographs are reviewed according to the modified Steinbrocker method by consensus of at least 2 rheumatologists. For this study radiographs that were scored as 4 were retrieved and rescored to indicate disorganization (4.0), subluxation (4.1), pencil-in-cup (4.2) and ankylosis (4.0). Subsequently, the clinical characteristics at first visit of patients who developed at least 1 joint with severe joint damage were compared to those without such damage.

Results: 664 patients who were enrolled  within 5 years of diagnosis were the subjects of this study. 116/664 (17.5%) were observed to have at least one joint with 4.0, 4.1, 4.2 or 4.3 of the 42 scored. The demographic and disease characteristics at first visit of the patients who were observed to develop such damage compared to those who did not are reported in table 1. Patients with severe joint damage were older at diagnosis of psoriasis and had longer PsA duration, but shorter psoriasis duration. They had higher active and damaged joint counts and ESR. There was a trend towards higher prevalence of female sex, axial disease and HLA-B*27 in those with severe damage. Of the 116 patients observed to develop severe damage, 34 (29%), 63 (54%), 36 (31%),  58 (50%) patients were observed to have ‘4.0′, ‘4.1′, ‘4.2′ and ‘4.3′, respectively at baseline or during follow-up. The mean (sd) number of joints with ‘4.0′, ‘4.1′, ‘4.2′ and ‘4.3′, were 0.3 (0.7), 1.1 (2.1), 0.6 (2.0) and 0.7 (1.4), respectively.  Only 15 (13%) patients were observed to have ankylosis without lysis. These patients had lower modified Steinbrocker score [mean, (sd) 31 (18) vs. 53 (43)      p=0.001] compared to those with subluxation or pencil-in-cup change.

Conclusion: Patients with PsA who develop severe joint damage have higher disease activity at presentation. The most common form of severe joint damage observed is subluxation. Only 13% have exclusive ankylosis. Further phenotypic characteristic of radiographic damage in PsA will facilitate genetic and mechanistic studies.

 Table 1. Demographics and Disease Characteristics at baseline

 

Variable	Patients with severe joint damage N=116	Patients without severe joint damage N=548	p-value
Gender (Males)	58 (50.0%)	322 (58.8%)	0.08
Age	43.8 (13.9)	41.7(12.9)	0.11
Age at diagnosis of Psoriasis	33.9 (15.5)	29.0 (14.6)	0.002
Age at diagnosis of PsA	41.4 (14.1)	39.8 (13.0)	0.27
Duration of Psoriasis	9.9 (10.1)	12.7 (11.6)	0.02
Duration of PsA	2.3 (1.6)	1.9 (1.7)	0.02
ESR	30.2 (20.5)	20.9 (19.6)	<0.0001
PASI score	6.3 (9.1)	5.9 (8.4)	0.76
Active joint count	12.9 (10.5)	9.4 (8.7)	0.001
Swollen joint count	5.7 (5.7)	4.7 (5.1)	0.09
Damage joint count	5.8 (5.2)	3.1 (4.0)	0.0008
Axial disease	41 (35.3%)	148 (27.0%)	0.07
HLA B*27	21 (22.6%)	59 (14.0%)	0.06
Follow-up time (radiographic visits)	11.6 (9.3)	5.3 (7.4)	<0.0001

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/severe-joint-damage-in-psoriatic-arthritis-mutilans-and-ankylosis/