Case description
A 64-year-old retired policeman presented with a 6-month history of intensely pruritic, painful, photosensitive erythematous plaques that gradually progressed to near-generalized psoriasiform lesions, initially misdiagnosed and unsuccessfully treated as psoriasis vulgaris.
On reevaluation, he had generalized violaceous-erythematous macules and plaques with white dry scale, erosions, excoriations, and xerosis, accompanied by classic dermatomyositis stigmata, including heliotrope rash, Gottron papules and Gottron sign, V-neck sign, shawl sign, holster sign, poikiloderma, mechanic’s hands (Fig 1, A-J), and an ovoid palatal patch. Calcinosis cutis was observed on both forearms. Dermoscopy and trichoscopy were supportive of dermatomyositis (Fig 2, A-D). Neurological workup revealed no subjective or objective muscle weakness.
Fig 1.
Clinical images of the face revealing (A) heliotrope rash and erythematous-violaceous macules on the nasolabial folds, (B) posterior hair line, (C and D) V-neck sign, (E) shawl sign and poikiloderma, (F) Gottron papules, (G) Mechanic’s hands, (H and I) holster sign, and (J) Gottron sign.
Fig 2.
A and B, Proximal nailfold dermoscopy revealed capillary telangiectasia, avascular area, and giant capillaries, (C) dermoscopy of Gottron papule revealed irregularly distributed dots and linear vessels surrounded by structureless white areas, and (D) scalp trichoscopy showed yellow dots, an interfollicular honeycomb pigment pattern, and thick linear, branching, and tortuous capillaries.
Laboratory studies demonstrated an elevated erythrocyte sedimentation rate (120 [2-30] mm/h), creatine kinase (239 [26-190] U/L), and lactate dehydrogenase (304 [91-232] U/L), with a high-titer speckled antinuclear antibody. Histopathological examination revealed interface dermatitis (Fig 3, A-D). Chest radiography, electrocardiography, and malignancy screening (prostate-specific antigen and carcinoembryonic antigen) were unremarkable.
Fig 3.
A-D, Histopathological findings show an interface dermatitis, atrophic epidermis with hyperkeratosis, parakeratosis, keratotic plaques, cytoid bodies, vacuolar degeneration of basal keratinocytes, focal pigment incontinence, and superficial dermal mucin deposition (Hematoxylin-eosin stain).
Combination therapy with tapering systemic corticosteroids, weekly methotrexate, and topical corticosteroids resulted in gradual improvement in erythema, scales, pruritus, and laboratory abnormalities over 6 months.
Question: Which myositis-specific autoantibody is most characteristic of this patient’s skin-predominant, intensely pruritic erythema with minimal clinical myositis?
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A.
Anti-Mi-2
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B.
Anti-MDA5
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C.
Anti-TIF1-γ
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D.
Anti-SAE
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E.
Anti-NXP2
Answer and discussion
The correct answer is anti-SAE. Anti-small ubiquitin-like modifier activating enzyme (anti-SAE) is a rare myositis-specific autoantibody that defines a distinct dermatomyositis subset with striking, often intensely pruritic, diffuse cutaneous erythema and psoriasiform or erythrodermic eruptions that may precede or occur in the absence of significant clinical myositis.1,2 The patient’s photosensitive violaceous erythema, heliotrope rash, Gottron papules and Gottron sign, V-neck and shawl signs, holster sign, poikiloderma, mechanic’s hands, and nailfold capillary changes are pathognomonic for dermatomyositis rather than psoriasis.1 Interface dermatitis with vacuolar alteration and dermal mucin further supports an autoimmune connective tissue process instead of psoriasiform hyperplasia or cutaneous T-cell lymphoma. Although calcinosis cutis and an ovoid palatal patch may be seen in other myositis-specific autoantibody subtypes such as anti-NXP2 and anti-TIF1-γ disease, respectively,1 this patient’s strongly positive anti-SAE antibodies with negative testing for other myositis-specific autoantibodies confirms classification as anti-SAE dermatomyositis.
Anti-SAE dermatomyositis is a rare myositis-specific autoantibody subtype, with reported prevalence generally below 10% across dermatomyositis cohorts.3 Anti-SAE positivity has been linked to mild muscle involvement, possible interstitial lung disease, and an increased risk of adenocarcinoma, warranting ongoing malignancy surveillance even when baseline screening is unrevealing.1,2 Mechanistically, SAE participates in SUMOylation, a post-translational modification regulating type I interferon signaling, NF-κB activation, and T-cell responses, offering a plausible explanation for the skin-predominant inflammatory phenotype in anti-SAE dermatomyositis.4,5 There are no treatment guidelines specific to this subset; management generally follows conventional dermatomyositis protocols, combining systemic corticosteroids with steroid-sparing immunosuppressants, such as methotrexate or mycophenolate mofetil.1
This case highlights that in older patients with treatment-refractory psoriasiform lesions, careful attention to photodistribution, dermatomyositis stigmata, supported by dermoscopy, histopathology, and early myositis-specific autoantibody testing, is essential to prevent misdiagnosis and facilitate timely immunosuppression and malignancy surveillance.
Declaration of generative AI and AI-assisted technologies in the writing process
None.
Conflicts of interest
None disclosed.
Footnotes
Funding sources: None.
Patient consent: The authors obtained written informed consent from the patient for the publication of the patient’s photographs and medical information to be published in print and online, with the understanding that this information may be publicly available. Patient consent forms were not provided to the journal but are retained by the authors.
IRB approval status: Not applicable.
References
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