Correspondence

Tinea Incognito

N Engl J Med 2000; 343:1499November 16, 2000

Article

To the Editor:

The photograph presented as a case of tinea incognito by Feder (July 6 issue)1 does not show features of tinea incognito. Tinea incognito is a mycotic infection of the skin that has been modified by systemic or topical treatment with steroids in a way that renders it no longer diagnostic. By contrast, the patient pictured in the article has a clear-cut cutaneous mycotic infection; in fact, the multiple, concentric erythematous rings with fine scaling are typical of tinea corporis. Patients with tinea incognito, by contrast, have patches, papules, or small nodules without the characteristic scaling of tinea corporis. The diagnosis of erythema migrans is also without foundation: erythema migrans is a nonscaly dermatosis and does not present with multiple concentric rings.

Lorenzo Cerroni, M.D.
University of Graz, A-8036 Graz, Austria

1 References

1
Feder HM Jr. Tinea incognito misdiagnosed as erythema migrans. N Engl J Med 2000;343:69-69
Full Text | Web of Science | Medline

Author/Editor Response

The author and a colleague reply:

To the Editor: Tinea incognito is a tinea infection whose appearance has been modified by the application of high-potency topical steroids. According to the original description,1 tinea incognito may present as inflammatory papules and pustules without the characteristics of tinea, as stated by Dr. Cerroni. In some cases, however, tinea incognito may retain the scaly appearance of tinea but be modified by local steroids so that it becomes extensive and bizarrely shaped,1 as happened in our patient.

The point of the case report was not the diagnosis of tinea incognito as opposed to tinea corporis but, rather, the misdiagnosis of erythema migrans. In Connecticut, where Lyme disease is endemic and a topic of heated debate,2 many annular rashes are misdiagnosed as erythema migrans.3 Before diagnosing Lyme disease, physicians need to consider other causes of annular eruptions such as tinea corporis and, when appropriate, perform potassium hydroxide examination or fungal culture. An annular rash that persists after a 20-day course of antibiotics, which would be appropriate for treating Borrelia burgdorferi infection, is not erythema migrans.

Henry M. Feder, Jr., M.D.
Diane M. Hoss, M.D.
Connecticut Children's Medical Center, Hartford, CT 06106

3 References

1
Ive FA, Marks R. Tinea incognito. BMJ 1968;3:149-152
CrossRef | Web of Science | Medline

2
Feder HM Jr. Differences are voiced by two Lyme camps at a Connecticut public hearing on insurance coverage of Lyme disease. Pediatrics 2000;105:855-857
CrossRef | Web of Science | Medline