Patch-type granuloma annulare: An institution-based study of 23 cases

Area of Science:

• Dermatology
• Pathology
• Immunology

Background:

• Granuloma annulare (GA) is a skin disorder with unknown causes.
• Patch GA is a rare subtype with limited available data.
• This study characterizes 23 patch GA cases.

Purpose of the Study:

• To describe the clinical and histopathologic features of patch GA.
• To differentiate patch GA from other dermatologic conditions.
• To improve the diagnosis and management of patch GA.

Main Methods:

• Retrospective review of dermatopathology archives for patch GA cases.
• Analysis of clinical history and morphology.
• Assessment of histopathologic features, including granulomatous inflammation patterns and cell types.

Main Results:

• Most patients were female (19/23) presenting with erythematous patches on the trunk and extremities.
• Common differential diagnoses included mycosis fungoides, morphea, and contact dermatitis.
• Histopathology revealed interstitial lymphocytes and histiocytes with dermal mucin; 1/3 of cases had eosinophils and plasma cells.

Conclusions:

• Patch GA is an uncommon variant with an interstitial granulomatous pattern, predominantly affecting women over 50.
• Clinically and histopathologically, it can resemble interstitial mycosis fungoides and early morphea.
• Recognizing patch GA aids in preventing misdiagnosis and inappropriate treatment.