Make the Diagnosis: Mysterious Skin Patches

Presentation

Case Findings: A 70-year-old man went to urgent care after becoming concerned about brown hyperpigmented patches on his legs and arms. He also thought that some of his teeth were turning gray, but it had been happening so slowly he wasn’t sure. He had been in good health recently, especially after starting on antibiotics last year to treat his rheumatoid arthritis.

What is your diagnosis?

Learnings

Drug-induced pigmentation caused by minocycline may affect the skin, mucosal surfaces, teeth, tongue, sclera, bone, heart, thyroid, and other locations. Minocycline is a tetracycline-derived antibiotic with various uses, most notably as a second-line treatment for acne vulgaris. Hyperpigmentation may follow ingestion of 100-200 mg/day for 1-3 years, and incidence rates vary from 2.4%-14.8%. However, some studies have demonstrated the development of hyperpigmentation following small doses and short courses of minocycline.

The incidence seems highest in patients with conditions such as atopic dermatitis, acne vulgaris, rheumatoid arthritis, pemphigoid, and pemphigus.

Four types of hyperpigmentation have been described: types I-IV. Each type varies in distribution and histology. (For type details, refer to Look For section.)

Pediatric Patient Considerations:

Children aged younger than 9 years should not be on medications from the tetracycline family of antibiotics.

What To Look For:

Well-circumscribed blue-gray, dirty-looking discoloration. There may be generalized and diffuse blue-gray discoloration affecting areas other than the skin, such as the oral cavity, tongue, teeth, and conjunctivae. Be vigilant in assessing for hyperpigmentation in dark-skinned patients, as it may be more difficult to detect minocycline-induced hyperpigmentation.

The 4 types of minocycline-related hyperpigmentation are:

• Type I: areas of facial inflammation, scars, and trauma
• • Type II: well-circumscribed patches on the arms and legs, or generalized discoloration away from areas of inflammation
  • • Type III: muddy-brown discoloration of sun-exposed areas
    • • Type IV: areas of scar tissue on the trunk

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Make the Diagnosis: Mysterious Skin Patches