IgG4-related sialadenitis (Mikulicz disease) is salivary gland involvement of IgG4-related systemic disease. It is characterized by bilateral parotid and submandibular gland enlargement; lacrimal gland involvement also frequently accompanies (previously Mikulicz syndrome). IgG4-related disease is a chronic inflammatory condition characterized by organ infiltration of IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis. Simultaneous involvement of salivary and lacrimal glands is the classic presentation. It is more common in males (M:F = 2-3:1). Mean age at diagnosis is 50-70. Serum IgG4 levels are generally elevated (>135 mg/dL) but may be normal in 20-30% of cases. Multisystemic involvement is frequent: autoimmune pancreatitis, retroperitoneal fibrosis, sclerosing cholangitis, thyroiditis, nephritis. Dramatic response to steroid therapy supports the diagnosis. Differential diagnosis with Sjögren syndrome is important — Sjögren shows anti-SSA/SSB positivity, sicca symptoms, and a different pattern.
Age Range
40-70
Peak Age
55
Gender
Male predominant
Prevalence
Rare
The imaging findings of IgG4-related sialadenitis are based on simultaneous IgG4-positive plasma cell infiltration and progressive fibrosis developing in all affected glands. Bilateral and symmetric gland enlargement reflects systemic immune dysregulation acting on all target organs simultaneously. Storiform fibrosis and obliterative phlebitis create structural changes in gland parenchyma and determine MRI signal characteristics. In early stages, inflammatory cellular infiltration causes T2 hyperintensity, while in advanced stages, fibrosis progression leads to T2 hypointensity — this stage-dependent signal change reflects disease activity. The 'salt and pepper' pattern on US results from focal inflammatory infiltration foci in the gland parenchyma creating heterogeneous echopattern. Simultaneous involvement of lacrimal and salivary glands has shown that Mikulicz disease and Küttner tumor, previously defined as separate clinical entities, actually reflect the same systemic disease involving different organs.
The most characteristic imaging finding for IgG4-related sialadenitis is bilateral symmetric parotid, submandibular, and lacrimal gland enlargement — known as the Mikulicz pattern. The combination of this finding with elevated serum IgG4 nearly confirms the diagnosis.
On T2-weighted sequences, IgG4-related sialadenitis shows bilateral gland enlargement with variable T2 signal characteristics. In the early active stage, inflammatory cellular infiltration causes T2 hyperintensity — increased free water and edema produce bright signal. In the advanced fibrotic stage, storiform fibrosis leads to T2 hypointensity — collagen accumulation reduces the free water proportion. This stage-dependent signal change reflects disease activity and response to steroid therapy. Symmetric enlargement and signal changes in bilateral parotid and submandibular glands is the most characteristic imaging finding of IgG4-related disease. Lacrimal gland T2 hyperintensity or hypointensity may be simultaneously observed.
Report Sentence
Both parotid and submandibular glands are symmetrically enlarged showing [hyperintense/hypointense] signal on T2-weighted sequences; bilateral involvement and symmetric enlargement are consistent with IgG4-related sialadenitis.
On B-mode ultrasonography, IgG4-related sialadenitis is characterized by a 'salt and pepper' pattern. This pattern consists of alternation between scattered small hypoechoic foci (inflammatory infiltrates) and echogenic dots (fibrotic and residual normal tissue) in the gland parenchyma. Symmetric enlargement and similar echopattern are seen in bilateral parotid and submandibular glands. Similar findings may be seen in lacrimal glands. Gland margins are generally smooth. Increased vascularity on Doppler indicates active inflammatory stage. This US pattern is highly specific for IgG4-related sialadenitis and is valuable for distinguishing from other causes of bilateral gland enlargement.
Report Sentence
Both parotid and submandibular glands are symmetrically enlarged with 'salt and pepper' pattern heterogeneous echopattern in the parenchyma; bilateral involvement and characteristic echopattern are consistent with IgG4-related sialadenitis.
On contrast-enhanced CT, IgG4-related sialadenitis appears as symmetric enlargement and homogeneous enhancement of bilateral parotid and submandibular glands. Gland margins are smooth and well-defined. Similar enlargement and enhancement may be seen in lacrimal glands. Periglandular fat planes are generally preserved — fat stranding of acute inflammatory sialadenitis is not prominent. Cervical lymphadenopathy may accompany reactively. CT is useful for evaluating accompanying pancreatic involvement (sausage pancreas), retroperitoneal fibrosis, and other organ involvement.
Report Sentence
Both parotid and submandibular glands are symmetrically enlarged with homogeneous enhancement on post-contrast series; bilateral symmetric involvement suggests IgG4-related disease.
On DWI, IgG4-related sialadenitis shows variable ADC values — dependent on disease stage. In the active inflammatory stage, cellular infiltration produces low-to-intermediate ADC values (0.8-1.3 × 10⁻³ mm²/s). In the advanced fibrotic stage, ADC values vary according to the degree of fibrosis. In response to steroid therapy, cellular infiltration decreases and ADC values rise — ADC is a valuable biomarker in treatment monitoring. Symmetric ADC values in bilateral glands support systemic disease.
Report Sentence
Diffusion restriction with symmetric ADC values is observed in bilateral parotid and submandibular glands; stage-dependent ADC change is consistent with IgG4-related sialadenitis.
On FDG PET-CT, IgG4-related sialadenitis shows low-to-moderate symmetric FDG uptake in bilateral glands (SUVmax typically 2-5). This uptake reflects inflammatory cell metabolism. It is generally distinguished from lymphoma (high FDG, SUVmax >8-10) by its lower uptake. PET-CT is useful for evaluating multisystemic involvement — pancreatic, retroperitoneal, lacrimal gland, lymph node, and other organ involvement can be detected in a single scan. FDG uptake decreases in response to steroid therapy.
Report Sentence
On FDG PET-CT, symmetric low-to-moderate FDG uptake is observed in bilateral parotid and submandibular glands; multisystemic IgG4-related disease should be evaluated and lacrimal gland, pancreas, and retroperitoneum should be checked.
Criteria
Bilateral parotid + submandibular + lacrimal gland involvement. Classic triad.
Distinct Features
Symmetric enlargement, dramatic steroid response, multisystemic screening mandatory.
Criteria
Salivary gland involvement alone, no lacrimal gland involvement.
Distinct Features
May overlap with Küttner tumor, single submandibular gland involvement possible.
Criteria
Salivary gland + ≥1 extra-salivary organ involvement (pancreas, retroperitoneum, biliary tract, kidney).
Distinct Features
Screening with whole-body PET-CT, multidisciplinary approach, long-term steroid/immunosuppressive therapy.
Distinguishing Feature
Lymphoma has very low ADC (<0.7), high FDG (SUVmax >8), solid mass or diffuse infiltration. IgG4 has intermediate ADC, low FDG, diffuse symmetric enlargement, steroid response.
Distinguishing Feature
Küttner tumor generally limited to submandibular gland, IgG4-related sialadenitis is multiglandular. Küttner may be IgG4-related but is the localized form.
Distinguishing Feature
Warthin may be bilateral but cystic-solid mixed in parotid tail, pertechnetate hot. IgG4 is diffuse gland enlargement, salt and pepper, no pertechnetate uptake.
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
Minor tükürük bezi biyopsisi veya kor biyopsi ile histolojik tanı. Serum IgG4 ölçümü. Steroid tedavi (prednizolon 0.6 mg/kg/gün, 2-4 hafta). Multisistemik tarama (pankreas, retroperitoneum, safra yolları). Steroid azaltma ve idame tedavi. Rekürrens %20-30.IgG4-related sialadenitis is a benign condition with dramatic response to steroid therapy. Diagnosis relies on the combination of serum IgG4, histology, and imaging. Steroid therapy (prednisolone 0.6 mg/kg/day) significantly reduces gland size within 2-4 weeks — this response supports the diagnosis. Multisystemic IgG4-related disease should be screened: pancreas (autoimmune pancreatitis), retroperitoneum, biliary tract, kidney, aorta, lung. Recurrence after steroid tapering occurs in 20-30%; rituximab is effective as second-line therapy. Differential diagnosis with Sjögren syndrome should be made clinically and serologically (anti-SSA/SSB, sicca symptoms). MALT lymphoma risk is low but should be considered in long-term follow-up.
Clinical correlation is required.