73 year-old woman with wide-spread plaques

The patient is a 73-year-old woman with a two month history of an eruption that began on the buttocks and thighs. It has spread to the arms. The clinical picture was not diagnostic, so biopsies have been done.

She is in her usual state of health.  There is no history of systemic illness. Her medications include: amlodopine, metooprolol, ASA, all for a number of years.  She had a tetanus booster a week before the onset of the rash.

I thought this would probably be indolent but she has has developed marked pruritus.  Because of her symptoms she was treated with fluocinolnide oinment. This had no effect. Doxycycline was not tolerated due to GI symptoms.

Laboratory studies were done. CBC and chemistries were within normal limits. Her Lyme tighter was negative.

Examination shows large plaques on the buttocks and thighs that they are now appearing on the arms. The remainder of the examination is unremarkable. 

Clinical Images:

Pathology:

Dermal interstitial proliferation of histiocytes with focally increased dermal mucin and increased dermal mucin.  Individual collagen fibers are circumferentially ringed with histiocytes.  The dermatopathologist  feels this is either interstitial granuloma annulare or interstitial granulomatous dermatitis.  Images courtesy of Lynne Goldberg, Boston University Skin Path.

 Diagnosis: Interstitial granuloma annulare versus interstitial granulomatous dermatitis.
There is one reference on PubMed to granuloma annulare following DT vaccination.

Reference:
1. A case of granuloma annulare in a child following tetanus and diphtheria toxoid vaccination.

Baskan EB, et. al. J Eur Acad Dermatol Venereol. 2005 Sep;19(5):639-40

What are your thoughts?