Dermoscopic features of ulcerated gouty tophus

ARTICLE

Auteur(s) : Yuichi Yoshida, Osamu Yamamoto

Division of Dermatology, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago-shi, Tottori 683-8503, Japan

Tophi (urate crystals) are most commonly seen on digits of the hands and feet in patients with gout and may be the initial manifestation of the disease [1]. Herein, we report the dermoscopic features of a case of ulcerated gouty tophus.

An 84-year-old Japanese man was referred to our hospital with a 1-month history of an ulcerative lesion on the right foot. Physical examination revealed an ulcerated nodule with whitish chalky material, 10 mm in size, on the right digit (figure 1A). A firm nodule with a red halo was also seen on the left digit. On dermoscopic examination, antler-like belts of whitish materials with some bright dots were recognized more clearly in the nodule (figure 1B). Histologically, there were amorphous eosinophilic materials with lymphohistiocytic cell infiltration in the dermis (figure 1C). Laboratory investigation revealed hyperuricemia (uric acid, 11.2 mg/dL). Based on these findings, a diagnosis of gouty tophus was made.

Gout is a systemic metabolic disease caused by the deposition of monosodium urate crystals in various tissues such as skin and bone [1]. Gout is clinically characterized by acute arthritis and tophus due to untreated hyperuricemia. Tophi commonly appear in digits of the hands and feet, auriculae and joints [2]. However, the number of patients with gouty tophus has been decreasing due to effective therapy, such as treatment with allopurinol. It is sometimes difficult to rule out other diseases, such as ruptured epidermoid cysts and rheumatoid nodules, and to make a correct diagnosis of gouty tophus, if it is the initial manifestation of the disease. It has been reported that radiological studies or polarized microscopic observation (needle aspiration) is useful for the diagnosis of gout, in addition to clinical and laboratory findings [1, 3].

Dermoscopy is now widely used as a useful tool for diagnosing many pigmented and non-pigmented skin tumors [4]. In the present case, it is of interest that there were antler-like belts of whitish materials with some bright dots on dermoscopic examination that were most likely to correspond to monosodium urate crystals in the ulcerated tophus. Similar dermoscopic features have recently only been reported in the Japanese literature [5]. However, it is not clear if they are detectable in non-ulcerated tophus.

Differential diagnosis by dermoscopy includes calcium deposition, calcifying epithelioma, keratoacanthoma and molluscum contagiosum. Those diseases have been described as having a whitish appearance in a Japanese textbook on dermoscopy [6]. However, bright dots seem only to be found in ulcerated gouty tophus. Therefore, gouty tophus could be included in the differential diagnosis of a whitish pattern on dermoscopy. Dermoscopy might provide additional clues to improve the diagnosis of gouty tophus.

Acknowledgements

References

2 Teng GG, Nair R, Saag KG. Pathophysiology, clinical presentation, and treatment of gout. Drugs 2006; 66: 1547-63.

3 Shimizu A, Tamura A, Ishikawa O. Finger pad tophi. Eur J Dermatol 2008; 18: 361-2.

4 Kittler H, Pehamberger H, Wolff K, et al. Diagnostic accuracy of dermoscopy. Lancet Oncol 2002; 3: 159-65.

5 Nakamura Y, Le Pavoux A, Ohara K. Gouty tophus of the tragus. Hifurinsho 2009; 51: 681-4; (in Japanese).

6 Ohara K. White lesion. In: Saida T, Ohara K, Tsuchida T, Tanaka K, eds. Color Atlas of Dermoscopy. Tokyo: Kanehara, 2003: 150-4; (in Japanese).