Coccygeal pad: a disease prevalent only in Japan?

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Arch Dis Child 2016;101:568
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Coccygeal pad: a disease prevalent only in Japan?

Y Yamaguchi, H Iwata, H Shimizu

Correspondence to Dr Hiroaki Iwata, Department of Dermatology, Hokkaido University Graduate School of Medicine, N15 W7, Kita-ku, Sapporo 060-8638, Japan;

A 5-year-old Japanese girl presented with a 3-year history of a brownish, rough-surfaced, elastic nodule along the spine. She was healthy and without any history of trauma such as prolonged bicycle riding or hard-chair sitting. MRI and physical examination revealed no musculoskeletal or neurological abnormalities such as sharply angulated joints. We considered human tail, coccygeal pad, meningioma and spina bifida. Of these, human tail and coccygeal pad have no contents in the nodule radiologically. Moreover, as coccygeal pad is an acquired lesion, whereas human tail presents as a congenital lesion, we diagnosed coccygeal pad.

A brownish, rough-surfaced, soft, elastic nodule of 4×2 cm presents on the sacrococcygeal area, with its long axis running along the spine.

Coccygeal pad is characterised as an acquired oval or tylosis-like nodule on the sacrococcygeal area consisting of proliferative collagen bundles resulting from chronic pressure or friction such as cycling or hard-chair sitting. In 1985, the first case was reported in the Japanese literature. Several cases are reported almost every year, and more than 50 cases have been reported. Only five cases have been reported in the English-language literature. All reported patients were ethnic Japanese living in Japan. Therefore, we hypothesised that the pathogenesis may relate, in part, to the Japanese lifestyle, which involves sitting or lying directly on tatami mats made from rice straw. In addition to chronic pressure, most cases had sacrococcygeal abnormalities, including sharply angulated joints or dislocation of the coccyx and spina bifida. These anatomical abnormalities occur worldwide; therefore, similar cases are expected to be observed outside Japan. Accordingly, we should make this condition more widely known.

Patient consent Obtained.

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