Background/Purpose

Several case reports and a few published studies suggest a link between Familial Mediterranean Fever (FMF) and ankylosing spondylitis (AS).  There is very limited data on the clinical features of AS that develops in patients with FMF. The aim of this study is to compare the demographic and clinical features of patients with AS in association with FMF to patients with AS alone.

Methods

73 patients with AS in coexistence with FMF (AS-FMF) who have been followed at 8 different hospitals were compared to 81 consecutive patients with AS alone from the same centers, in regard with demographic and clinical features. All of the patients fulfilled the modified New York criteria for AS and the patients with FMF additionally met the Livneh criteria for FMF. Patients’ demographic and clinical data including latest disease activity (BASDAI) and functional status (BASFI) were extracted from patients’ charts; MEFV genotypes, HLA B27 status and C reactive protein levels and radiographic results were also recorded if available. The independent t test was used to compare differences in continuous data. Comparisons of categorical data between groups were tested using the chi-square test

Results

Patients in the AS-FMF group were younger and had a shorter disease duration. Gender distribution and age of onset of AS were similar in both groups; but diagnostic delay was longer and family history (for SpA) was reported more frequently in the AS group. Peripheral arthritis and heel enthesitis were more prevalent among AS-FMF patients, whereas a higher proportion of patients in the AS group had HLA-B27 and had radiographic evidence of spinal involvement.  BASDAI and BASFI and the other spondyloarthritis related features were not different between the two groups. Demographic and clinical features of the patient groups are summarized in the Table below. M694V allelic variation was detected in 78.7% of the patients who had both AS and FMF.

Conclusion

Clinical characteristics of AS in association with FMF may show some differences from typical AS, such as less spinal involvement.  However, this finding may also be, at least partially, explained by shorter disease duration in this group of patients. Relatively higher prevalence of M694V variant among patients who have both FMF and AS, than those reported in the historic FMF cohorts; as well as the lower prevalence of HLA-B27 in this group than those previously reported in Turkish AS patients suggest that such genetic differences may be accounted for some of the differences between the patients with AS alone and those with AS in association with FMF.

Table. Demographics, and clinical features of the patient groups

Features	AS (n:81)	FMF-AS (n:73)	P
Age, mean ± SD	45± 12.4	37 ± 11.9	<0.001
Male gender    n; %	54; 66.7	49; 67.1	Not significant
Disease duration,  mean± SD	10 ±8.2	6 ±5.8	0.007
Age of onset of back pain,  mean ± SD	24± 8.4	23 ± 9.9	Not significant
Age of diagnosis of AS, mean ± SD	36± 12.2	30 ± 11.2	0.013
Diagnostic delay,  mean ± SD	11 ±13.0	6 ±6.0	0.002
Smoking status, n (%)	52/78 (66.7)	46/72; 63.9 63.0%	Not significant
Peripheral artrhritis , n; %	20/79; 24.7%	49/71; 69.0 67.1%	<0.001
Heel enthesitis, n; %	32/79; 40.5 39.5%	43/72; 58.9	0.018
Dactylitis, n; %	1;1.2	3; 4.2	Not significant
Acute anterior uveitis, n; %	10; 12.3%	11; 15.06%	Not significant
Psoriasis, n; %	1; 1.3	2; 2.7	Not significant
Inflammatory Bowel Disease, n; %	1; 1.3	0	Not significant
Family History (excluded FMF) , n; %	32; 39.5%	18; 24.7%	0.02
BASFI, mean ± SD	3.1± 2.3	3.5 ± 2.5	Not significant
BASDAI,    mean ± SD	3.7± 2.5	4.2 ± 2.7	Not significant
CRP mg/L,    mean ± SD	11± 13.0	15± 29.0	Not significant
HLA B27 positivity, n; %	45/63; 71.4	17/67; 25.4	<0.001
Syndesmophytes any , n; %	31/55 (56.4)	18/54 (33.3)	0.016

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-characteristics-of-ankylosing-spondylitis-in-association-with-familial-mediterranean-fever-with-those-of-typical-ankylosing-spondylitis/