Details
74-year old male patient with a posterior neck lesion.
Interstitial granulomatous dermatitis is a rash that presents with erythematous and violaceous plaques that may be painful and pruritic. This entity is strongly associated with systemic diseases, including rheumatoid arthritis, systemic lupus erythematosus and other connective tissue disorders. The patient’s clinical history was notable for rheumatoid arthritis.
Sections show a spongiotic lesion, with brisk peri-vascular, peri-follicular and interstitial inflammation, with mostly lympho-histiocytic infiltrates composed of T-cells (CD3+) and histiocytes (CD68+). Focal areas of leukocytoclasis and necrosis are also seen.
Dermal mucin was not increased (based on Hales colloidal iron stain findings) and the basement membrane was not thickened (PAS finding), two findings that can be seen with connective tissue disease.