Case Number : Case 2561 - 30 April 2020 Posted By: Saleem Taibjee

Infiltrate is heavier in deeper dermis, no significant necrobiosis or well formed palisade, numerous eosinophils and single collagen fibers surrounded by histiocytes (floating sign). I would consider Interstitial granulomatous dermatitis. 

1 hour ago, Meenakshi Batrani said:

1 hour ago, Meenakshi Batrani said:

Infiltrate is heavier in deeper dermis, no significant necrobiosis or well formed palisade, numerous eosinophils and single collagen fibers surrounded by histiocytes (floating sign). I would consider Interstitial granulomatous dermatitis. 

Agree 

Granuloma annullare, interstitial type. 

Lots of eos. 

I will also raise the possibility of interstitial granulomatous drug reaction

30 minutes ago, Dr. Mona Abdel-Halim said:

Lots of eos. 

I will also raise the possibility of interstitial granulomatous drug reaction

agree

Yes, I too favoured interstitial granulomatous drug reaction. As per comments above, eosinophils are quite conspicuous, this also a nice example of the 'free floating collagen' sign. I omitted to indicate that the clinician had actually suggested granuloma annulare. However, the anatomical site (axillae) is actually quite good for IGDR, other sites of predilection including inner aspects of upper arms, inner thighs and groin region. Such sites are not common for typical GA. Histological clues to distinguish from GA can include presence of interface involvement in some cases of IGDR and absence of necrobiosis or increased mucin. However, such cases depend on clinical correlation. There are numerous possible causative rugs including calcium channel blockers, ACE inhibitors, beta blockers, lipid-lowering drugs, diuretics, NSAIDs, andtihistamines, anticonvulsants, antidepressants, allopurinol and methotrexate. It is also important to highlight to the clinician that IGDR is one example of a drug reaction in which there can be a long latency from onset of the rash after commencement of the rash, and similarly, only a slow resolution on stopping the drug i.e. the drug should not be re-started too soon before concluding whether or not it may be the culprit. A further differential diagnosis is interstitial granulomatous dermatitis/neutrophilic palisaded granulomatous dermatitis spectrum, as associated with systemic disease such as connective tissue disease. However, eosinophils would be unusual in that context.