Typical herpes zoster lesions with dermatomal distribution on blue skin base due to topical application of ink.

What is the diagnosis?

Diagnosis
The unilateral dermatomal distribution of the lesions, their vesicular nature, and the preceding sensory symptoms locally suggest the diagnosis of herpes zoster. Of special interest was the fact that these lesions appeared on blue skin base, rather than the typical erythematosus skin base.

Teaching points
- The patient initially denied the application of any treatment on the lesions. However, after persistent questioning he admitted applying ink over the rash following the advice of his children's pediatrician that he phoned earlier the day of presentation to us (Figure 1).

- Herpes zoster (shingles) results from reactivation of latent varicella -zoster virus (VZV) within the sensory ganglia. The diagnosis is made upon clinical criteria. The dermatomal pattern of distribution and the appearance of the herpes zoster rash are so distinctive that the diagnosis is usually obvious. However, various circumstances may modify the expected appearance of the lesions. For example, in our case application of ink caused the appearance of herpes zoster lesions on a blue skin base instead of the typical erythematosus base. In cases where the diagnosis is in doubt, polymerase chain reaction (PCR) techniques are the most sensitive and specific diagnostic tests [1]. Serologic confirmation is rarely needed [1,2].

- Ink has been traditionally used in several countries, including Greece, as a mild antinflammatory and antiseptic agent. Nowadays its use has been decreased; it can be used as a diagnostic tool in cases of suspected scabies where the application of ink to an area of rash could make burrows become evident [3].

Acknowledgements
The case was prepared by Drs. V. German, G. Sakagiannis, and G. Margaritis; it was submitted for consideration for publication.

References
1. Mounsey AL, Matthew LG, Slawson DC. Herpes zoster and postherpetic neuralgia: prevention and management. Am Fam Physician. 2005;72:1075-80.
2. Opstelten W, van Loon AM, Schuller M, van Wijck AJ, van Essen GA, Moons KG, Verheij TJ. Clinical diagnosis of herpes zoster in family practice. Ann Fam Med. 2007;5:305-9.
3. Brodell RT, Helms SE. Office dermatologic testing: the scabies preparation.
Am Fam Physician. 1991;44:505-8.