A 70-year-old woman is referred for evaluation of a chronic foot rash. She states that the rash was first noted 2 years ago and has been asymptomatic. Her medical history is positive for hypertension and severe rheumatoid arthritis, the latter of which has been treated with etanercept for 20 years. She denies a history of diabetes.
Several weeks ago, she developed a skin infection and was placed on an oral antibiotic; during the 2-week course of the antibiotic and the subsequent month, etanercept therapy was discontinued. The patient notes that her foot condition improved considerably during this 6-week period. Physical examination reveals a well-demarcated erythematous plaque of the dorsal and medial surface of her right foot. Rheumatoid nodules were noted on several fingers.
Submit your diagnosis to see full explanation.
Interstitial granulomatous dermatitis (IGD) is an uncommon skin disorder that is poorly defined in the medical literature.1 The dermatitis is characterized by the appearance of an erythematous and indurated plaque; less than 10% of cases present in a rope-like distribution (“rope sign”),2 which was once considered pathognomonic.1,3 Lesions are usually asymptomatic.
The condition was first described as a reactive disease associated with arthritis.4 Subsequent cases have been linked to myeloproliferative diseases, systemic lupus, and medications. Similar to this case, IGD has been reported in patients with rheumatoid arthritis treated with the tumor necrosis factor-alpha (TNF-α) inhibitor etanercept.5
Histopathology may aid in diagnosis revealing a predominant CD68-positive macrophage infiltrate distributed between collagen bundles of the mid and deep dermis.2 Although the majority of cases resolve spontaneously, about 30% persist or relapse.2 Resolution has been reported following treatment with dapsone, hydroxychloroquine, and cyclosporine.6
1. Tebeica T, Voicu C, Patterson JW, et al. Interstitial granulomatous dermatitis (IGD). Open Access Maced J Med Sci. 2017;5(4):543-544. doi:10.3889/oamjms.2017.120
2. Peroni A, Colato C, Schena D, Gisondi P, Girolomoni G. Interstitial granulomatous dermatitis: a distinct entity with characteristic histological and clinical pattern. Br J Dermatol. 2012;166(4):775-783. doi: 10.1111/j.1365-2133.2011.10727.x
3. Tomasini C, Pippione M. Interstitial granulomatous dermatitis with plaques. J Am Acad Dermatol. 2002;46(6):892-899. doi: 10.1067/mjd.2002.120532
4. Cases-Merida S, Lorente-Lavirgen A, Pérez-Gil A. Interstitial granulomatous dermatitis due to a rare myeloproliferative neoplasia. Indian J Dermatol. 2018;63(3):264-267. doi: 10.4103/ijd.IJD_432_17
5. Hu S, Cohen D, Murphy G, Mody E, Qureshi AA. Interstitial granulomatous dermatitis in a patient with rheumatoid arthritis on etanercept. Cutis. 2008;81(4):336-338.
6. Walling HW, Swick BL. Interstitial granulomatous dermatitis associated with chronic inflammatory demyelinating polyneuropathy. Cutis. 2012;90(1):30-32.