When a Painful Rash Keeps Recurring: A Case of Seronegative Amyopathic Dermatomyositis Without Neurological Sequelae

We present a case of seronegative amyopathic dermatomyositis (SADM). This clinical entity should be considered in the differential diagnosis of patients with recurring, painful erythematous skin manifestations, and requires close monitoring for the development of neurological manifestations and malignancy. SADM is a rare autoimmune disease that affects the skin and muscles. It is considered a subtype of dermatomyositis (DM), which is a systemic autoimmune disease. The exact cause of SADM is not fully understood but is believed to involve a complex interplay between genetic, environmental, and immunological factors. The diagnosis of SADM is typically made based on clinical evaluation, blood tests, muscle biopsy, and skin biopsy. Treatment options for SADM may include corticosteroids, immunosuppressive drugs, and other supportive measures to manage symptoms and prevent disease progression. A 30-year-old female presented with symptoms of intermittent burning, painful rash primarily on the hands and face. Her medical history was remarkable for a six-year history of multifocal joint pain, chronic low back pain, and intermittent, painful recurring rash in the upper body (face, neck, and chest). Neurological examination revealed scalp tenderness and arthralgia in the upper extremities, with normal motor strength examination. Skin findings included described an erythematous rash on the arms and hands bilaterally. Skin punch biopsy showed compact orthokeratosis, atrophy of the epidermis, interface changes, and increased dermal mucin on the colloidal iron stain, which are suggestive of DM. Electromyography and nerve conduction study were normal. The MRI of the left thigh was normal. C3 and C4 levels were reduced. The extended muscle-specific myositis panel including MDA5 was negative. The patient was placed on a multidrug regimen, including methotrexate, hydroxychloroquine, and prednisone. Within one year of follow-up, she was found to have reductions in skin manifestation and flare-ups. Clinicians should consider amyopathic DM (ADM) in the differential diagnosis of patients with recurring, painful skin manifestations. This condition can be easily overlooked as the development of neurological sequelae may be present much later in the course. We highlight the need for a multi-disciplinary management approach for patients with this unique diagnosis. Close monitoring for the development of neurological manifestations and associated sequelae including malignancy is recommended.