IgG4-Related Cutaneous Vasculitis Presenting as Multiple Subcutaneous Nodules.

Area of Science:

• Pathology
• Immunology
• Dermatology

Background:

• Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition.
• Cutaneous manifestations of IgG4-RD are diverse but often underrecognized.
• Obliterative phlebitis is a known feature of IgG4-RD, but its presentation in subcutaneous nodules is less common.

Purpose of the Study:

• To report a unique case of IgG4-related disease presenting as subcutaneous nodules.
• To highlight the histopathological features and diagnostic criteria for IgG4-RD in this context.
• To emphasize the importance of considering vascular involvement in cutaneous IgG4-RD.

Main Methods:

• Histopathological examination of excised subcutaneous nodules.
• Immunohistochemistry for IgG4-positive plasma cells and IgG:IgG4 ratio.
• Exclusion of other potential etiologies, including neoplasms and infections.

Main Results:

• Histopathology revealed a well-circumscribed intravascular lesion with lymphoplasmacytic infiltrate, histiocytes, and eosinophils.
• Immunohistochemistry confirmed >200 polytypic IgG4+ plasma cells/high-powered field and an IgG4:IgG ratio >0.5.
• Diagnosis of IgG4-related disease with obliterative phlebitis of a medium-sized subcutaneous vein was established.

Conclusions:

• This case expands the classification of cutaneous IgG4-related disease.
• It underscores the significance of recognizing vascular manifestations in IgG4-RD.
• Broader awareness of these presentations is crucial for timely diagnosis and management.