O/E: The is a solitary 10 cm ring-shaped plaque on the right arm. Sensaton to pinprick is normal.
Diagnosis: Interstitial Granulomatous Dermnatitis (IGH) vs. Granuloma annulare.
The patient lives in an endemic region for Lyme disease. His work takes him to Asia, South America, the Mid-East, and all parts of North America. Presently, he is in Iraq and will have a Lyme serology when he returns. Certainly, the clinical picture could suggest erythema migrans, but an eight month history would be unusual. There are a host of case reports of IGH in association with arthritis, collagen vascular disease, inflammatory bowel disease and even Lyme disease; but they are hard to make sense of. (Guilt by association?) Although we see erythema chronicum migrans with regularity in New England, this lesion did not jump out as typical to me; but in retrospect, it could be the interface between IGH, GA and ECM. An old ECM? Food for thought. How long will the primary lesion of Lyme disease remain without treatment. Eight months seems a long time.
IGD is a distinct entity with a typical histological and clinical pattern. The importance and the nature of the association with extracutaneous diseases remains to be clarified. Patients should be screened for rheumatic and autoimmune diseases.