Interstitial granulomatous dermatitis (IGD) has been associated with pharmacotherapy, various autoimmune conditions, and hematologic malignant conditions. Herein, we report a patient in whom IGD was the initial manifestation of a previously undiagnosed myeloma.
A man in his 50s presented with a 1-year history of an asymptomatic symmetric eruption involving his upper back, arms, forearms, and hands. His medical history was significant for arthritis, diabetes mellitus, hypertension, and a retroperitoneal schwannoma that was excised with negative margins 1 month prior to presentation. His medications included metformin, telmisartan, naproxen, and vitamin B6.
On physical examination, he had erythematous to violaceous patches and plaques, some with a slight trailing scale (Figure 1). One of the lesions on his right forearm was infiltrated and had an annular border. Multiple punch biopsy specimens were obtained for further investigation and revealed an interstitial lymphohistiocytic infiltrate extending into the upper and mid-reticular dermis (Figure 2) with some associated elastophagocytosis. A CD68 immunostain revealed histiocytes intercalated among the collagen bundles. An increase in mucin was not appreciated, and there was no associated necrobiosis. A diagnosis of IGD was made, and further workup to determine an underlying cause was performed.
The erythematous plaque shows a slight trailing scale.
A, Normal epidermis overlying a subtle, low-density, interstitial, histiocytic dermal infiltrate and mild perivascular lymphoid inflammation (original magnification ×110). B, Low-density dermal infiltrate of CD68+ histiocytes intercalate interstitially among collagen bundles (original magnification ×660).
Results of a complete blood cell count, comprehensive metabolic panel, and urinalysis were unremarkable. He tested negative for antinuclear antibodies, anti-Ro/SS-A, anti-La/SS-B, p-ANCA, c-ANCA, and rheumatoid factor. An immunofixation electrophoresis (IFE) revealed an increased IgA level and M-spike with an IgA-κ reading too small to be quantified.
The patient was referred to hematology, and a bone-marrow biopsy was performed. His marrow was infiltrated with 20% to 25% of IgA-restricted plasma cells, and the patient was subsequently diagnosed with stage 1 myeloma. He began treatment with bisphosphonate, and his skin disease resolved shortly after presentation without recurrence. His myeloma progressed over the course of 3 years, and he underwent bone-marrow transplantation.
Interstitial granulomatous dermatitis usually presents between ages 50 and 60 years, with a female predominance.1 Clinically, there are multiple asymptomatic papules and plaques on the proximal limbs and trunk, and in a few patients, cordlike lesions can be seen, distinctively known as the “rope sign.”1 Histologically, IGD is characterized by an interstitial arrangement of histiocytes in the reticular dermis often surrounding foci of degenerated collagen.1 Extracutaneous manifestations may precede, occur simultaneously, or follow the development of the skin lesions.1 Interstitial granulomatous dermatitis has been associated with various hematologic malignant conditions including myelodysplastic syndrome,2 leukemia,3 and lymphoma.1 The prognosis of IGD is favorable, with two-thirds of patients maintaining complete remission after 3 months to 3 years, and therapy does not seem to alter the disease course.1
This is the first case, to our knowledge, of IGD as the initial presentation of myeloma. This case highlights the importance of a thorough systemic workup to detect not only an autoimmune disease but also an underlying hematologic malignant condition in patients who present with IGD. As part of the routine workup in these patients, we advocate the use of the more sensitive IFE testing to detect an underlying paraproteinemia.
Corresponding Author: Sabra Abner, MD, Division of Dermatology, Department of Medicine, The University of Louisville School of Medicine, 3810 Springhurst Blvd, Ste 200, Louisville, KY 40241 (firstname.lastname@example.org).
Published Online: June 3, 2015. doi:10.1001/jamadermatol.2015.1160.
Conflict of Interest Disclosures: None reported.
Disclaimer: Dr Callen is associate editor of JAMA Dermatology, but he was not involved in any of the decisions regarding review of the manuscript or its acceptance.
Thompson L, Abner S, Malone J, Callen JP. Interstitial Granulomatous Dermatitis as the Initial Manifestation of Myeloma. JAMA Dermatol. 2015;151(10):1141–1142. doi:10.1001/jamadermatol.2015.1160