Dermoscopy and imaging findings of disseminated cutaneous gout: A rare manifestation of a common disease

Dear Editor, Gout is a common metabolic disease with the deposition of monosodium urate crystals in the synovial fluid and skin overlying the articular sites.[1] However, extensive skin involvement by gouty tophi is an extremely rare presentation. In this report, we present the clinical, dermoscopic, and imaging findings of two patients with disseminated cutaneous gout. In case 1, a 56-year-old man presented with multiple tender firm nodules on the extremities for 8 years. He had a medical history of gout diagnosed since young adulthood. Physical examination showed multiple yellow-whitish nodules on the shins, calves, and arms [Figure 1a and b]. Dermoscopic examination showed ovoid pale-to-bright yellow globules encompassed by either peripheral erythema or branching vessels [Figure 1c and d]. A laboratory survey revealed elevated serum uric acid level (7.9 mg/dL). Radiography showed numerous tiny foci of mineralization in the left calf [Figure 1e]. Soft-tissue ultrasound demonstrated well-defined, irregularly shaped, heterogeneous hyperechoic structures with a hypoechoic rim in the dermis with posterior acoustic shadowing. In shear wave elastography mode, these structures had increased stiffness compared to the surrounding tissues [Figure 1f]. Skin biopsy revealed amorphous eosinophilic material in the reticular dermis and subcutis surrounded by lymphohistiocytic infiltrates and multinucleated giant cells [Figure 1g]. Four months later, the skin lesions remained stationary despite treatment with benzbromarone and colchicine.Figure 1: (a) Indurated yellow-whitish nodules on the anterior shins arranged in clusters, (b) Deposition of firm nodules along the right extensor hallucis longus tendon. Dermoscopic examination showed, (c) Ovoid-shaped homogeneous yellow globules surrounded by peripheral erythema and, (d) Larger pale yellow globules encompassed by branching vessels, (e) Left lower leg plain film (anterior-posterior view) showed multiple tiny foci of mineralization in the left leg, (f) Shear wave elastography mode soft-tissue ultrasound demonstrated heterogeneous hyperechoic substance with peripheral hypoechoic rim and posterior acoustic shadowing, characterized by increased stiffness (blue color) compared to the surrounding tissues, (g) Histopathologic examination showed amorphous eosinophilic crystals in the reticular dermis with focal lymphocytic infiltrate (H and E, ×100).In case 2, a 60-year-old man presented with widespread, tiny, milia-like round papules on the extremities for 6 months. He had a medical history of gouty arthritis for 7 years. Physical examination showed multiple yellow, firm papules on the upper and lower limbs and buttocks [Figure 2a and b]. Dermoscopy revealed light yellow to white round milia-like globules with a peripheral erythematous halo [Figure 2c]. Blood tests showed hyperuricemia (12.9 mg/dL). Incisional biopsy demonstrated mid-dermal amorphous pink crystalline substances surrounded by focal lymphohistiocytic infiltrates [Figure 2d]. Negatively birefringent needle-shaped crystals were found under polarized light microscopy [Figure 2e]. A diagnosis of miliarial gout was confirmed. Unfortunately, the patient died 3 months later due to septic shock induced by acute pancreatitis and toxic epidermal necrolysis.Figure 2: (a and b) Milia-like firm papules appeared in crops on the left forearm and the right thigh, (c) Dermoscopy showed light yellow round milia-like globules surrounded by an erythematous halo, (d) Histopathologic examination showed amorphous pink substances in the mid dermis with focal lymphohistiocytic infiltrate (H and E, ×100), (e) Polarized microscopy revealed negatively birefringent needle-shaped crystals in the dermis (×100).Although gout is a prevalent metabolic disorder, disseminated cutaneous gout with widespread tophi deposited in extra-articular regions is a very rare clinical manifestation. Miliarial gout is an extremely rare intradermal variant of cutaneous gout, characterized by numerous milia-like papules composed of cream-colored substances dispersed on an erythematous base.[2] With the advancement of technology, innovative tools can assist in the noninvasive diagnosis of gout. On plain films, gouty tophi manifest as soft-tissue density masses, with 50% of cases showing radio-opaque calcific deposits.[3,4] Ultrasound can detect the presence of tophi, characterized by a hyperechoic heterogeneous center with an anechoic/hypoechoic halo.[5] In our patients, dermoscopic examination revealed yellowish globules surrounded by erythematous halo or branching vessels. The peripheral erythematous halo may correlate with focal inflammation. The branching vessels may correspond to the extensive vasculature encircling the gouty deposits, which is consistent with previous studies using color Doppler ultrasound demonstrating hypervascularity around the tophi.[4,6] These vascular structures tend to be distributed around larger gouty nodules, indicating their need for a more abundant blood supply. Previously, the dermoscopic features of cutaneous gout have only been described in one case report. Yoshida and Yamamoto found antler-like belts of whitish materials and bright dots in a case of ulcerated gouty tophus.[7] In comparison, dermoscopic examination of nonulcerated cutaneous gout in our cases demonstrated homogeneous yellow materials without similar antler-like belts or bright dot structures. These distinct dermoscopic characteristics may be explained by the different disease subtypes of cutaneous gout (ulcerated vs. nonulcerated). Overall, dermoscopy is a noninvasive tool that aids in the differential diagnosis of skin diseases sharing similar clinical presentations with cutaneous gout [Supplementary Table 1].[5,7-21] A clinical algorithm for patients who present with multiple disseminated yellow-white cutaneous papules or nodules is shown in Supplementary Figure 1. A limitation of this report is the small case number, and further investigations with a greater number of patients are required to verify the dermoscopic and imaging findings of disseminated cutaneous gout.Supplementary Table 1: Dermoscopic and imaging findings of skin diseases with similar clinical presentation to disseminated cutaneous goutSupplementary Figure 1: Clinical algorithm for patients who present with multiple disseminated yellow-white cutaneous papules or nodules.In this report, we present two patients with disseminated cutaneous gout, a rare clinical manifestation of a common disease. Cutaneous gout can be visualized as soft-tissue masses with calcifications on radiography, hyperechoic heterogeneous substances with hypoechoic rim on ultrasound, and homogeneous pale-to-bright yellow globules with erythematous halo or branching vessels on dermoscopy. Clinicians should be aware that a subset of patients with long-standing gout may present with disseminated skin disease, and dermoscopy in combination with radiography and ultrasonography may assist in the noninvasive diagnosis of this disease entity. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published, and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Data availability statement Data sharing not applicable to this article as no datasets were generated or analyzed during the current study. Financial support and sponsorship Nil. Conflicts of interest Prof. Stephen Chu-Sung Hu, an Associate Editor at Dermatologica Sinica, had no role in the peer review process of or decision to publish this article. Dr. Kuan-Yu Chu declared no conflict of interest in writing this paper.