Clinical Characteristics and Burden of IgG4-Related Disease in the United Arab Emirates

Keywords

IgG4 syndrome - IgG4-RD - IgG4-related autoimmune disease - IgG4-related sclerosing disease

Introduction

First identified in the early 2000s, immunoglobulin G4-related disease (IgG4-RD) represents a class of immune-mediated disorders with distinct pathological features, including dense lymphoplasmacytic infiltration, storiform fibrosis, obliterative phlebitis, and often elevated serum IgG4 levels.[1] [2] The disease is known for affecting various organs, including the salivary glands, orbits, lymph nodes, pancreas, hepatobiliary system, kidneys, and the retroperitoneal space.[1] [3]

Globally, IgG4-RD has been documented across several regions, with significant variation in its clinical presentation, demographic features, and affected organs.[4] [5] Most reports have emanated from cohorts in the United States, Europe, and Asia, highlighting variations in patient characteristics and disease manifestations.[3] [6] [7] Despite this global recognition, literature addressing IgG4-RD in the Middle East and North Africa (MENA) region remains limited. Only a few studies, including a prior case cohort from our institution in the UAE, have explored the clinical attributes of IgG4-RD in this population.[8] This study aims to address this gap by presenting a follow-up investigation into the clinical features and burden of IgG4-RD within the Emirati population, emphasizing the need for establishing a national registry to accurately assess disease prevalence and raise awareness among both health care professionals and the general public in the UAE. In this study, we focus on the clinical and demographic characteristics of IgG4-RD within a cohort of Arab patients treated at a tertiary care center in the UAE.

Patients and Methods

Subjects

We retrospectively analyzed data from patients diagnosed with IgG4-RD at our facility between April 1, 2015 and May 31, 2023. To identify cases, we searched our electronic medical records database using the keywords “IgG4-RD,” “retroperitoneal fibrosis,” and “raised serum IgG.” Eligible patients were those older than 18 years who had attended at least two follow-up visits with the rheumatology clinic within a 6-month time frame. Patients younger than 18 years, those who missed follow-up visits, had significant missing laboratory data, or had other forms of inflammatory arthritis were excluded. Diagnosis of IgG4-RD was determined using both the ACR/EULAR 2019 criteria and the comprehensive diagnostic criteria. A total of 28 patients met at least one of these diagnostic standards.

Study Variables

A comprehensive review and analysis of the electronic health records of all patients were conducted to extract data on demographics, medical history, laboratory results, and treatment information. Comorbidities such as dyslipidemia, hypertension, diabetes mellitus (DM), thyroid disorders, chronic kidney disease (CKD), coronary artery disease, gastrointestinal issues, nonmalignant blood disorders (like iron deficiency anemia, sickle cell anemia, and thalassemia), asthma, chronic obstructive pulmonary disease, osteoporosis, depression, and malignancies were documented. Recorded laboratory investigations included rheumatoid factor (RF), anti-CCP, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), immunofluorescence antinuclear antibody (IF-ANA), anti-Ro/SSA, anti-La/SSB, double-stranded DNA (dsDNA), C3, and C4. Medication details were also gathered, covering the use of oral corticosteroids, conventional synthetic disease-modifying antirheumatic drugs (DMARDs) like hydroxychloroquine, methotrexate, azathioprine, and mycophenolate mofetil, along with biologic DMARDs such as rituximab.

Statistical Analysis

Descriptive statistics, such as means, medians, and percentages, were used to describe the characteristics of the cohort. Continuous variables are presented as mean ± standard deviation, while skewed continuous variables are summarized using median ± standard deviation. Statistical analyses were performed using R 3.2.2 (R Foundation for Statistical Computing, Vienna, Austria).

Results

Baseline Characteristics

A total of 28 Arab patients were diagnosed with IgG4-RD, with 82% hailing from the UAE, 7% from Egypt, and 4% each from Jordan, Syria, and Sudan. The median age at the onset of symptoms was 42 ± 3 years (median ± SD), and the median age at diagnosis was 47 ± 4.6 years, reflecting a 5-year gap between the initial presentation and diagnosis. Most patients were males (57%), resulting in a male-to- female ratio of 4:3. Of the 28 patients, 23 (82%) had a biopsy-confirmed diagnosis of IgG4-RD ([Table 1]).

Table 1 Baseline clinical characteristics of Emirati patients with IgG4-related disease

Characteristics	Value
No. of cases, n	28
Gender (M:F)	4:3
Median age at the symptom's onset (y ± SD)	42 ± 3
Median age at the time of diagnosis (y ± SD)	47 ± 4.6
Biopsy, n	23
BMI (median ± SD)	28 ± 28
Smoking (%)	43
Comorbidities
DM (%)	32
Hypertension (%)	36
Thyroid disease (%)	25
Dyslipidemia (%)	32
Cardiac disease (%)	4
Chronic kidney disease (%)	25
Gastrointestinal disease (%)	15
Hematological disease (%)	43
Osteoporosis (%)	7
Pulmonary disease (%)	11
Psychiatry (%)	7
Malignancy (%)	7
Atopy (%)	45
Clinical manifestations
Lower back pain (%)	54
Flank pain (%)	36
Mid thoracic back pain (%)	7
Lymphadenopathy (%)	29
Shortness of breath (%)	7
Vision changes (%)	11
Constitutional symptoms (%)	71
Oliguria or anuria (%)	36
Mass location
Renal pelvis or/and Ureter (%)	46
Aorta (%)	18
Exocrine gland (%)	18
Pancreatic and biliary ducts (%)	7
Ocular (%)	11
Pituitary/CNS (%)	7
Laboratory
ESR (mm/h), median ± SD	70 ± 32
CRP (mg/L), median ± SD	25 ± 28
Eosinophilia, median ± SD	0.24 ± 0.10
IF-ANA (%)	14
Rheumatoid factor (%)	13
Anti-CCP (%)	0
SSA/SSB (%)	4
Smith Ab (%)	0
Low C4 (%)	4
Low C3 (%)	11
Elevated ds DNA (%)	4
RNP-Ab (%)	4
c-ANCA and p-ANCA	0
Serum IgG4 (mg/dL), median ± SD	1.3 ± 1.2
Prior infections
Hepatitis A (%)	0
Hepatitis B (%)	4
Hepatitis C (%)	0
History of VZ infection (%)	0
Latent TB infections (%)	17
Imaging modality
CT chest (n)	7
CT abdomen and pelvis (n)	19
MRI brain (n)	2
MRI abdomen and pelvis (n)	3
PET/CT (n)	1
Biopsy findings
Marked lymphocytic and plasmocytic infiltration (%)	54
Storiform fibrosis (%)	24
Ratio of IgG4/IgG > 40% (%)	11
IgG4-positive plasma cells/HPF >10 (%)	21
Management
Prednisone (%)	93
Methotrexate (%)	29
Hydroxychloroquine (%)	7
Azathioprine (%)	36
Mycophenolate mofetil (%)	18
Rituximab (%)	36
Outcomes
Alive (%)	100

Abbreviations: BMI, body mass index; CNS, central nervous system; CRP, C-reactive protein; CT, computed tomography; DM, diabetes mellitus; ESR, erythrocyte sedimentation rate; IF-ANA, immunofluorescence antinuclear antibody; IgG4, immunoglobulin G4; MRI, magnetic resonance imaging; PET, positron emission tomography; SD, standard deviation; TB, tuberculosis; VZ, varicella-zoster virus.

Comorbidities and Modifiable Risk Factors

Among the cohort, 43% patients were smokers, and the average body mass index (BMI) at diagnosis was 28 kg/m². The most frequent comorbidities were hematological disorders (43%), dyslipidemia (32%), hypertension (36%), DM (32%), thyroid disease (25%), and CKD (25%).

Additional comorbidities included atopy (45%), gastrointestinal disorders (15%), pulmonary diseases (11%), malignancies (7%), and depression (7%; [Table 1]).

Clinical Manifestations and Organ Involvement

The most common symptoms reported were constitutional symptoms, affecting 71% of the patients, followed by low back pain in 54%, attributed to mass effect. Oliguria, anuria, and flank pain were present in 36% of cases, while 29% had lymphadenopathy and 11% reported vision changes. Only 7% experienced mid-thoracic back pain or shortness of breath. Regarding organ involvement, 89% of patients had a single organ affected, with the kidneys being the most frequently involved (46%), primarily impacting the renal pelvis and/or ureter. This was followed by the aorta (18%) and exocrine glands (19%). Two-organ involvement, such as kidneys and lymphadenopathy, was noted in just 11% of the cohort ([Table 1]).

Inflammatory Markers, Autoantibody Profile, Imaging, and Biopsy Findings

At baseline, the median ESR and CRP levels were 70 ± 32 mm/h (normal range: 0–20 mm/h) and 25 ± 28 mg/L (normal range: <5 mg/L), respectively. The median serum total IgG was 15.7 g/L, and the IgG4 levels were 1.3 ± 1.2 g/L. Autoantibody screening revealed that 13% patients had a positive RF, 14% had positive IF-ANA, while ds-DNA, SS-A, and RNP-Ab positivity were found in 4% of cases each. Additionally, 11% had low C3 levels, and 4% had low C4. Other autoimmune markers, such as SS-B, anti-CCP, c-ANCA, and p-ANCA, showed no significant results. Diagnostic imaging, including chest, abdomen, and pelvis computed tomography (CT) scans (with and without contrast), was performed in all patients. Seven patients underwent chest CT, 19 had CT of the abdomen and pelvis, 2 had brain magnetic resonance imaging (MRI), 3 had MRI of the abdomen and pelvis, and 1 patient had a positron emission tomography (PET)/CT scan. Tissue biopsies, confirming the diagnosis of IgG4-RD, were conducted in 23 out of 28 patients. Key biopsy findings included lymphocytic and plasmocytic infiltration (54%), storiform fibrosis (24%), the presence of more than 10% IgG4-positive plasma cells per high-power field (21%), and an IgG4-to-total IgG ratio greater than 40% in 11% of cases.

Medications

Upon diagnosis, 93% of patients were started on oral prednisone, with doses ranging from 0.5 to 1 mg/kg, adjusted according to symptom severity and tapered over time. Azathioprine was the most commonly prescribed DMARD, used by 36% of patients, followed by methotrexate (29%). Other DMARDs included mycophenolate mofetil (18%) and hydroxychloroquine (7%). Among biologic DMARDs, rituximab was the most frequently used, prescribed to 36% of patients ([Table 1]).

Discussion

IgG4-RD demonstrates a wide spectrum of clinical manifestations that vary significantly based on geographic, genetic, and environmental factors.[9] Our study of IgG4-RD in the UAE provides a unique opportunity to compare and contrast findings with other cohorts globally and from the Middle East ([Table 2]), where data on this condition remain limited. This analysis builds on prior findings from Türkiye and Saudi Arabia and contributes to understanding the clinical characteristics and burden of IgG4-RD in this region.[7] [10]

Table 2 Comparison of the clinical characteristics of the IgG4-related disease cohorts in the literature

Cohort (reference) variables	UAE[8]	Türkiye[7]	United States[6]	United States[13]	Spain[14]	Spain[11]	France[18]	Italy[19]	Japan[12]	China[20]	UK[21]
No. of patient	15	52	125	57	55	15	25	41	235	118	28
Male-to-female ratio	4:3	1:1	1.6:1	1.7:1	3:1	4:1	2.6:1	1.9:1	4:1	2.3:1	26 (92%) M
Age at diagnosis (y)	Median: 47 ± 4.6	Mean: 51.1 ± 12.7	Mean: 50.3 ± 14.9	Mean: 58 ± 14.8	Median: 53	Median: 60.7 ± 14.8	Mean: 58	Median: 62	Median: 67	Mean: 53.1	Mean: 58.2 ± 14.2
Mean disease duration prior diagnosis (y ± SD)	5	NA	5.0 ± 7.5	NA	NA	NA	3.8	NA	NA	NA	NA
Main comorbidities	Hematologic al, gastrointestinal, cardiovascular, allergic (45%)	Endocrinological	NA	NA	Endocrinological	NA	NA	Allergic, gastrointestinal (30%)	Allergic, endocrinological (39%)	Allergic (61.8%)	Cardiovascular, respiratory
Main organs involved	RPF, aorta and exocrine glands	RPF, pancreas	Submandibular glands, lymph nodes, orbits, pancreas	Pancreas (26.4%), pericardium, gallbladder, liver	RPF (27%), orbital pseudotumor (22%), salivary gland (16%), pancreas (16%)	Lymph nodes (60%), kidneys (40%), salivary glands (33.3%), pancreas (20%)	Lymph nodes (76%), pancreas (52%), salivary glands (44%), kidney (44%), biliary duct (32%), RPF (32%)	Pancreas, RPF	Pancreas (61%), salivary glands (34%), kidneys (23%), exocrine glands (23%), aorta (20%)	Lymph nodes (65.3%), salivary glands (64.4%), exocrine glands (50.8%), pancreas (1%)	Pancreas (60%), biliary tree (25%), liver (10.7%), salivary gland (6%), lymph nodes (6%), lungs (5%)
IgG4 ≥135 mg/dL (%)	67	67.3	51.4	12	NA	682.33	52	73	470	97.5	21
Serologies	ANA (14%), RF (13%), low C3 (11%), low C4 (4%)	ANA (7%) MPO-ANCA	Low C3 (20%), low C4 (19%)	NA	NA	Low C3 and C4 (33.3%)	ANA (16%), low C3 and/or C4 (56.25%)[*]	ANA (17%), low C3 and/or C4 (14%)	ANA with ≥40 titers in 50% and ≥80 in 23%	Positive ANA 11%	ANA (6%), ANCA (1%), low C3 (6%), low C4 (5%)
Biopsy (%)	82	25	100	100	100	67	100	75	64	57.6	65
Biopsy finding		NA	NA						NA	NA
Marked lymphocytic and plasmacytic infiltration (%) Storiform fibrosis (%) Ratio of IgG4/IgG > 40% (%) IgG4-positive plasma cells/HPF >10 (%)	54 25 11 21			94.7 68.4 NA NA	100 93.3 Median: 126.7 Median: 223	80 10 NA 50	92 80 NA Number: 8	NA NA Mean: 0.4 ratio Number: 25			NA 93.3 NA 92.9
Glucocorticoids (%)	93	71	51	45.6	85.5	100	92	100	69	96.6	100
DMARDS (%)	89	57.5	36.8	MTX 14.3 AZA 14.3	34.5	33.3	48	41	NA	60.1	16
DMARDS used	MTX, HCQ, AZA, MMF	MTX, AZA, CYC	MTX, MMF, tamoxifen, AZA, CYC, IVIG	MTX, AZA, RTX	MTX, AZA, MMF, CYC, RTX	Tacrolimus, MTX, RTX	MTX, AZA, RTX, CYC, TOC, tamoxifen, imatinib	MTX, AZA, RTX, CYC	NA	NA	AZA
Rituximab (n)	10	24	7	5	3	1	3	1	0	0	0

Abbreviations: ANA, antinuclear antibody; AZA, azathioprine; BMI, body mass index; C3 and C4, serum complement 3 and 4; CYC, cyclophosphamide; DMARDs, disease-modifying antirheumatic drugs; IVIG, intravenous immunoglobulin; MTX, methotrexate; NA, not available; RPF, retroperitoneal fibrosis; RTX, rituximab.

^* Analyzed on 16 patients only.

When considering the demographic profile of our cohort, the median age of diagnosis (47 years) was notably younger than that in global cohorts such as Japan (67 years) and Spain (60 years).[11] [12] However, this is consistent with the data from Türkiye and Saudi Arabia, where the median ages of diagnosis were 53 and 49 years, respectively.[7] [10] This trend may reflect earlier disease recognition or diagnosis in the Middle Eastern populations, potentially due to the increased awareness and access to tertiary care centers. Alternatively, genetic or environmental factors may play a role in the earlier onset of disease in this region.

The male predominance seen in our cohort (57% male) is in line with findings from other studies in the Middle East. The Turkish cohort reported a male-to-female ratio of 1.5:1, while a Saudi cohort also indicated a higher male prevalence, with a male-to-female ratio of approximately 2:1.[7] [10] This mirrors international findings, such as those from Japan and the United States, where men are more frequently affected than women.[6] [12] The consistent male predominance across both global and regional cohorts suggests that gender-related differences in IgG4-RD are universal, although the reasons for this disparity remain unclear.

Organ involvement is another critical aspect of IgG4-RD, and our findings provide valuable insights into regional patterns. In our study, the kidneys were the most commonly affected organ, seen in 46% of patients, followed by retroperitoneal involvement. This is consistent with findings from the Turkish cohort, where renal and retroperitoneal involvements were also frequently observed.[7] In contrast, cohorts from Japan, the United States, and the United Kingdom report more frequent involvement of the pancreas and salivary glands.[6] [12] [13] This discrepancy could be due to regional differences in genetic predispositions or environmental factors influencing organ-specific manifestations. Further studies investigating genetic and environmental risk factors for organ involvement are necessary to clarify these observations.

Our cohort showed a relatively high percentage of patients with constitutional symptoms (71%), such as fatigue, fever, and low back pain (54%), which are likely linked to the mass effect of retroperitoneal fibrosis. Similarly, the Turkish cohort reported fatigue in 67% of patients and back pain in 40%.[7] These similarities highlight the significant systemic burden of IgG4-RD in the Middle Eastern populations. Comparatively, other international cohorts, particularly from Europe, have reported lower frequencies of these systemic symptoms, suggesting potential regional variations in disease severity or progression.[14]

Laboratory findings in our cohort were consistent with global and regional data. Elevated ESR and CRP levels were observed in the majority of patients, with median ESR levels of 70 mm/h and CRP of 25 mg/L. These inflammatory markers are often elevated in active IgG4-RD and are consistent with findings from Türkiye, where the mean ESR was 62 mm/h.[7] Additionally, the UAE cohort had a notable proportion of patients (14%) with low complement levels (C3 and C4), similar to what has been observed in the Japanese and European cohorts.[12] [15] The presence of low complement levels is often associated with more severe or multisystemic disease, which may indicate a more aggressive disease phenotype in our region.

Histopathological findings in our study align with the established diagnostic criteria for IgG4-RD. Biopsy-proven diagnoses were present in 82% of patients, and histological features such as storiform fibrosis and lymphoplasmacytic infiltration were commonly observed. This is consistent with findings from Saudi Arabia and Türkiye, where histopathological confirmation was achieved in 75 to 80% of patients.[7] [10] These findings underscore the importance of histopathological confirmation for accurate diagnosis, particularly in regions where IgG4-RD is less well recognized. The use of tissue biopsy in most cases aligns with global diagnostic guidelines, which emphasize its role in confirming IgG4-RD.[1] [2]

Treatment strategies in our cohort largely mirrored international practices. The vast majority of patients (93%) received oral corticosteroids as initial therapy, consistent with treatment protocols worldwide.[15] [16] Notably, our cohort had a high rate of rituximab use (36%) as a steroid-sparing agent. This is in line with international findings, where rituximab has been increasingly recognized as an effective therapy for patients with refractory or relapsing disease.[17] In the Middle East, rituximab has also gained prominence, particularly in patients with severe or multi-organ involvement.[7] [10] The use of DMARDs such as azathioprine and methotrexate was consistent with regional and international data, with these agents used to maintain remission and minimize corticosteroid-related side effects.[6] [16]

Despite the smaller sample size of our cohort, this study contributes significantly to the understanding of IgG4-RD in the Middle East. Comparisons with regional data from Türkiye and Saudi Arabia[6] [10] show that IgG4-RD in the UAE presents similarly in terms of demographics, organ involvement, and treatment outcomes. However, the lower rates of pancreatic involvement and higher rates of renal and retroperitoneal disease in our cohort suggest possible regional variations in disease expression. These findings highlight the need for larger, multicenter studies to further explore these patterns and identify potential genetic or environmental factors contributing to these differences.

Conclusion

The establishment of a national or regional IgG4-RD registry would be invaluable in providing more accurate prevalence data and enhancing clinical awareness of this disease in the Middle East. Such a registry could facilitate more extensive research on the epidemiology and clinical spectrum of IgG4-RD in Arab populations, ultimately improving diagnostic and therapeutic strategies in this region.

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