Minocycline hyperpigmentation isolated to the subcutaneous fat

Area of Science:

• Dermatology
• Histopathology
• Pharmacology

Background:

• Minocycline is frequently prescribed for acne vulgaris.
• Minocycline-induced hyperpigmentation is a known side effect, typically affecting the dermis.
• Type II minocycline hyperpigmentation is characterized by blue-gray to brown pigmentation.

Observation:

• A 15-year-old female presented with bilateral lower extremity discoloration.
• The discoloration persisted for one year during minocycline treatment for acne.
• Clinical presentation suggested type II minocycline hyperpigmentation.

Findings:

• Histological examination revealed pigmentation exclusively in the subcutaneous adipose tissue.
• The dermis was completely spared from pigmentation.
• Special stains for iron were negative, an unusual finding for this type of pigmentation.

Implications:

• This case represents the first documented instance of pigment deposition solely in subcutaneous fat.
• The negative iron stain challenges typical understanding of minocycline hyperpigmentation mechanisms.
• Further research is needed to elucidate the pathogenesis of this unique presentation.