[Perforating granuloma annulare with transfollicular perforation]

Area of Science:

• Dermatology
• Pathology

Background:

• Perforating granuloma annulare (PGA) is a rare variant of granuloma annulare.
• Clinical diagnosis of PGA is challenging, often requiring histological confirmation.
• Unique localization occurs in less than 10% of cases.

Observation:

• A 36-year-old woman presented with a year-long solitary, ulcerated nodular lesion on her upper arm.
• Clinical and biological evaluations were unremarkable.
• Histological examination revealed perforating granuloma annulare with significant epidermal ulceration.

Findings:

• Histopathology confirmed perforating granuloma annulare with a large epidermal ulceration.
• Evidence of hair follicle infiltration and destruction suggested transfollicular elimination of necrotic material.
• Other conditions with palisading granuloma histology were excluded.

Implications:

• The solitary nature of the lesion prompted differential diagnosis including cutaneous tuberculosis, mycobacteriosis, sarcoidosis, foreign body granuloma, and carcinoma.
• The exact pathophysiology and perforation mechanism in PGA remain unclear.
• Treatment outcomes for PGA are variable, highlighting the need for further research.