A report of the first case of Dirofilaria infection in the eyelid region in Japan.

Dirofilaria worms were recovered from a painless hard tumor in the right eyelid of a 19-year-old Japanese male who had lived in Kagoshima and Kumamoto Prefectures, Japan. In the worms, the cuticle had a smooth surface, the inner cuticular layer had internal lateral longitudinal ridges, and the musculature of the body wall was the polymyarian type. On the basis of all morphological characteristics observed, this worm was identified as an immature female Dirofilaria immitis. This is the first human case of nematode infection in the eyelid in Japan. Surgical removal of the mass with worms resulted in complete recovery from swelling of his right eyelid.