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How to identify IgG4-related diseases? The director imparts the criteria for classification and diagnosis

 Last Update: 2022-10-25
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IgG4-RD not only loves to simulate other diseases, but is also often simulated
by other diseases.

IgG4-related disease (IgG4-RD) is a newly recognized and complex immune disease in recent years, which is characterized by elevated serum IgG4 with multi-organ damage, which is one of the rare diseases that seriously threaten the health of
patients.

However, because IgG4-RD is often simulated with tumors, connective tissue diseases and other diseases, IgG4-RD is missed, misdiagnosed or overdiagnosed
clinically.

Fig.
1 Missed diagnosis and misdiagnosis vs overdiagnosis
of the 9th Children's Rheumatic Immunity Summit Forum and the 15th National Pediatric Rheumatic Immune Disease Study Class were recently held
online.
At the meeting, Professor Zhang Wen from Peking Union Medical College Hospital gave an explanation on the differential diagnosis of IgG4-RD, focusing on the simulation of IgG4-RD for malignant tumors and hematological diseases from the case point of view, and briefly described the overlap between
IgG4-RD and connective tissue disease.

Classification diagnostic criteria for IgG4-RD Before learning the differential diagnosis, Let's first understand the classification and diagnostic criteria for IgG4-RD by ACR and EULAR in 2019: 1.
The admission criteria
have clinical or imaging features of typical organ involvement:

pancreas, lacrimal glands/large salivary glands, bile ducts, orbits , kidneys, lungs, aorta, retroperitoneum, dura or thyroid.

2.
Exclusion criteria include clinical, serological, pathological non-IgG4-RD features and known diseases that mimic IgG4-RD:
Table 1 Exclusion criteria

for IgG4-RD 3.
Each item was scored, and different weights
were scored according to histopathological characteristics (tissue changes and IgG4 infiltration), serum lgG4 level and affected organs, and the cumulative weight score ≥ 20 can be diagnosed as IgG4-RD
.

Tumor mimics IgG4-RD When tumor mimics IgG4-RD, IgG4-RD findings may be reactive or present as paraneoplastic syndromes
.
Professor Zhang Wen started from the case and provided the differential diagnosis idea
of tumor simulation IgG4-RD.

Case one

Female, 47 years old, chest tightness, breath holding for more than 3 months, aggravated by 1 month
.

CT with contrast: anterior mediastinal mass, bilateral pleural effusion, rapid growth
.

ESR 40 mm/h, C-reactive protein (CRP) 62 mg/L, IgG 19.
9 g/L, IgG4 2630 mg/L
.

3 biopsies
.
Puncture and thoracoscopy: hyperplasia of fibrous connective tissue, focal infiltration of perivascular lymphocytes
.
Consistent with chronic sclerosing mediastinititis
.
Composition: CD21(+), CD20(+), CD3(+), CD4(+), CD8(+), CD138(+), IgG4>10/HPF, gG4+/IgG+ about 30%.

Treatment: prednisone 50 mg QD, cyclophosphamide (CTX) 100 mg Qod
.
After 1 week, chest tightness and breath holding were significantly relieved, ESR, CRP, IgG and IgG4 returned to normal, pleural fluid decreased, and mediastinal mass shrunk
.

However, after 3 months of prednisone 30 mg/day, the mediastinal mass increased again, and platelets decreased to 20×10⁹/L
.
Bone puncture: lymphoma
.

Summary of identification points:

IgG4+/1gG+＜30%；
poor response to treatment;
Pleural fluid grows rapidly;
Unexplained thrombocytopenia
.

Case two

Male, 60 years old, bilateral parotid gland area enlargement for more than
1 year.

A subcutaneous mass in the left parotid gland area 1 year ago, progressively enlarged
.
Resection pathology: multifocal chronic inflammatory cell infiltration of subcutaneous tissue, chronic inflammation
of salivary gland tissue.
Postoperative wound is locally red and swollen
.
After half a year, the right parotid gland area is red and swollen, and the subcutaneous induration is knotted
.

Assay: lgG 25.
16g/L, lgG4 5300mg/L
.

Pathological: parotid gland: acinar atrophy, infiltration of multiple lymphocytes and plasma cells
.
There are many flaky infiltrated lymph, plasma cells and histiocytes around the dermis and subcutaneous blood vessels, and some areas of panniculitis-like changes, and lymphocytes have certain atypia.

CD3, CD20, CD68, CD38, Kappa, Lamda(+), CD30 scattered, Ki67 30%, IgG4>50/HPF, IgG4/gG>50%.

TCR rearrangement and other tests: panniculitis T lymphoma
.

Summary of identification points:

The lesion extends beyond the glandular boundaries;
Pathologic shows cellular atypia
.

Case 3
male, 40 years old; Lower limb numbness, backache in November, aggravated in
February.

Before November, both lower limbs were numb, painful, and accompanied by soreness
in the lower back.
Examination: retroperitoneal mass, left hydronephrosis, lumbar spine destruction
lumbar 2 vertebral biopsy: consistent with IgG4-RD, methylprednisolone (MP) 20 mg, ineffective
.
Formal anti-tuberculosis treatment for another 5 months was still ineffective
.
Repeat biopsy: lumbar + retroperitoneal, both consistent with IgG4-RD
.

Since 2 months ago, the numbness and weakness of both lower limbs have worsened, and the muscle strength of the lower limbs has reached grade
0.
MP 250 mg pulse was given locally, and 4 intrathecal injections were ineffective
.

Auxiliary examination on admission: normal blood and urine routine; ESR＞140mm/h，hsCRP 92.
15mg/L，IgG 18.
03g/L，IgG4 2570mg/L，T-IgE 179KU/L，T-SPOT.
TB: 364 SFC/10S6MC, Yu (-).

CT: T2 to L2 segment peri-aorta soft tissue; L2 vertebral body destruction
.

Diagnosis and treatment outcome: After admission to our hospital, FDG-PET/C found 1.
4cm nodule at the tip of the right lung of T, SUVmax 8.
34, and pulmonary nodulectomy was performed after multidisciplinary consultation
.
Pathological diagnosis: inflammatory myofibroblastoma (IMT).

A few days after surgery, the patient's ESR and CRP decreased significantly, and the muscle strength of the lower limbs gradually recovered, and the muscle strength returned to grade
IV within 1 month.

Summary of identification points:

IgG4-RD vertebral body involvement is rare, but common sites such as salivary glands and lacrimal glands are not affected;
Pathological: more myofibroblast infiltration, ALK (+);
Histochemistry: IgG4/IgG<40%;
Moderate to high-dose hormonal therapy does not respond well, and new lung mass
.

Hematologic diseases mimic IgG4-RD1

Luo Dao's diseaseSinus histiocytosis with giant lymphadenopathy (SHML) is an unexplained benign histioproliferative disorder that can occur in or outside the lymph nodes of organs or tissues
.
Its characteristic pathological changes are:

Under low-magnification lesions, the light-stained area and the deep-stained area alternately exist, forming nodular lesions;
The lightly stained area is composed of hyperplastic large histiocytes;
The lymphoid and plasma cells that proliferate next to it form a deep stained area;
Extension phenomenon (Emperinolesis): histiocytes are rich in cytoplasm, and phagocytes, plasma cells, eosinophils or neutrophils can be seen in the cytoplasm;
Immunohistochemistry: S100, CD68(+)

Rodao disease simulating IgG4RD is more common in men, mainly extralymphadenopathy, dura mater and dura mater, and swelling and sclerosis
of other organs.
Blood IgG4 level is mildly to moderately increased, histopathological IgG4 number and IgG4/IgG ratio are critical, and there is a characteristic protrusion phenomenon, S100(+).

Stiae fibrosis and phlebitis obliterans are rare
.
Response to treatment is slightly worse
.

2Erdheim-Chester disease (ECD)ECD is lipogranulomatosis and is a non-Langerhans histiocellular disorder
.
Its characteristics are:

More common in adult males;
59-70 years old;
Bones, heart, lungs, retroperitoneal, periorbital, skin, etc.
are affected;
Characterized by foam macrophage aggregation, chronic inflammation, fibrosis and organ failure;
A large number of foamy (xanthelasma) histiocytes infiltrate tissues, inflammatory cells and multinucleated giant cells, fibrosis mixed in or wrapped out, CD68, CD163(+).

The overlap of IgG4-RD with other diseases So far, there is still controversy
in the community about the overlap of IgG4-RD with other diseases.
Is this an overlap syndrome? Or is one of the diseases a secondary change to the other? Or is it a simulation between the two?
Overlap between IgG4-RD and ANCA-associated vasculitis has been reported and defined as a new overlap syndrome
.
There are also reports of overlap
between IgG4-RD and Castleman disease.
However, this definition is not widely accepted, and we look forward to more studies in the future to define the relationship
between IgG4-RD and these diseases.
"
Summary:
IgG4-RD is often simulated with a variety of diseases, such as tumors, connective tissue diseases, hematological diseases, chronic infections and other diseases, which can easily lead to high diagnosis and misdiagnosis rates or overdiagnosis
.
Clinicians need to be proficient in the triage diagnostic criteria for IgG4-RD, with exclusion criteria being particularly important
in the differential diagnosis.

Expert profileProfessor
Zhang Wen, Peking Union Medical College Hospital

Professor and doctoral supervisor of Peking Union Medical College Hospital
Deputy Director, Department of Rheumatology and Immunology
Member and Secretary of the Chinese Rheumatology Branch
Vice Chairman of Beijing Rheumatology Branch
Vice Chairman of the Rheumatology and Immunology Branch of the Chinese Association of Women Physicians
Member of the Standing Committee of the Rheumatology Branch of the Chinese Medical Doctor Association
Leader of the IgG4-RD Group of Rheumatology and Immunology of the Cross-Strait Health Exchange Association
Member of the International Diagnostic Standards for IgG4-Related Diseases

References:

[1] LIU Hang,YANG Jiaoting,XIAO Weiguo,ZHANG Wen.
Interpretation of "2019 ACR and EULAR IgG4-related Disease Classification Criteria" J.
Chinese Journal of Clinical Immunology and Allergy,2019,13(06):447-453.

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