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Hyperpigmentation associated with oral minocycline

Insights

Minocycline treatment can cause blue-black leg pigmentation due to iron-containing granules within macrophages. These granules may also contain minocycline degradation products, impacting skin histology.

Area of Science:

  • Dermatology
  • Histopathology
  • Toxicology

Background:

  • Minocycline is an antibiotic used to treat various infections and inflammatory conditions.
  • Skin pigmentation is a known, though uncommon, side effect of minocycline therapy.

Observation:

  • Two patients receiving minocycline presented with blue-black pigmentation on their legs.
  • Biopsies of the affected skin revealed the presence of pigment granules.

Findings:

  • The granules contained iron, exhibiting staining properties similar to melanin.
  • A third, unidentified pigment, possibly a minocycline degradation product, was also observed.
  • Electron microscopy indicated that granules were primarily within macrophages, some being membrane-bound.
  • Analytical electron microscopy confirmed the presence of iron, sulfur, and chlorine within the granules, with calcium noted in one instance.

Implications:

  • This study elucidates the histopathological basis of minocycline-induced hyperpigmentation.
  • Understanding the composition of these pigment granules aids in diagnosing and managing this side effect.
  • Further research may clarify the exact nature of the minocycline degradation product and its role in pigmentation.

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