Primary congenital lymphedema is the rarest form of primary lymphedema. Lymphedema of the extremities presents at birth and rarely involves the genitalia. There has never been a reported case in Thailand. The authors herby report a case of a 6-year-old boy who presented with progressive swelling of the lower legs since birth. The edema progressed into his scrotum and his arms. There was no history of lymphangitis or cellulites. Physical examination revealed a generalized non-pitting edema of all extremities, more on the right leg than the left leg. Swelling of the scrotum and penis was also detected. A diagnosis of primary congenital lymphedema was confirmed with lymphoscintigraphy.

Keywords: Primary congenital lymphedema, Scrotal edema, Lymphoscintigraphy