SHM Converge Scientific Abstract ePoster Gallery-Rare Case of Merkel Cell Carcinoma-Induced Dermatomyositis

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This case describes a 48-year-old Caucasian woman with hypothyroidism who developed a 6-month history of rash involving the face, neck, chest, arms, and thighs, initially treated as a perfume allergy without improvement. She also developed arthralgias and myalgias. On exam, she had classic dermatomyositis findings including Gottron papules, shawl and holster signs, periungual erythema, telangiectasias, and dilated capillary loops, while muscle strength remained intact.<br /><br />Laboratory testing was negative for multiple autoimmune and myositis markers, including ANA, SSA/SSB, Jo-1, Mi-2, SRP, MDA-5, NXP-2, anti-TIF1, and muscle enzymes (CK, aldolase), as well as inflammatory markers. Skin biopsy from the hands showed dermatitis with dermal mucin deposition, supporting dermatomyositis. Because dermatomyositis can be paraneoplastic, CT chest/abdomen/pelvis was performed and revealed left inguinal lymphadenopathy. Biopsy of this node demonstrated a high-grade neuroendocrine carcinoma with CK20 dot-like positivity, consistent with Merkel cell carcinoma (MCC) of unknown primary. PET imaging showed hypermetabolic left inguinal lymph nodes.<br /><br />She was treated initially with prednisone, then hydroxychloroquine and weekly methotrexate were added as steroid-sparing therapy. For MCC, she received carboplatin and etoposide, but had an allergic reaction to etoposide. Pembrolizumab was started as second-line therapy with a good tumor response, though it triggered a flare of dermatomyositis that required temporary holding of immunotherapy and restarting prednisone. After improvement, prednisone was tapered while hydroxychloroquine and methotrexate were continued. Follow-up PET showed decreased metabolic activity in the pelvis and inguinal nodes.<br /><br />This report emphasizes that dermatomyositis may signal an underlying malignancy, and MCC should be included in the differential diagnosis when evaluating new-onset dermatomyositis.

Asset Subtitle

Babray Laek

Meta Tag

Author List Babray Laek, Zuhal Arzomand

Category Clinical Vignettes

Concept Dermatomyositis

Concept Paraneoplastic Syndrome

Concept Merkel Cell Carcinoma

Concept Malignancy Screening

Concept Malignancy

Distinguished Non-Finalist

Presenter Organization UPMC McKeesport

Presenting Author Babray Laek

Track Adult

Keywords

dermatomyositis

Merkel cell carcinoma

paraneoplastic syndrome

Gottron papules

high-grade neuroendocrine carcinoma

inguinal lymphadenopathy

pembrolizumab

skin biopsy

autoimmune markers

PET imaging

Dermatomyositis

Paraneoplastic Syndrome

Merkel Cell Carcinoma

Malignancy Screening

Malignancy