Lymphoedema caused by idiopathic lymphatic thrombus

Primary lymphoedema includes some diseases whose genetic anomaly is detected and others whose pathology is unknown. In this article, we report a lymphatic thrombus found in a limb with lymphoedema during lymphatico-venous anastomosis (LVA). A 32-year-old man was aware of oedema in his left calcar pedis 3 years previously, which appeared without any trigger. Indocyanine green lymphography indicated lymphatic stasis in the left calf and thigh region, and we performed LVA for the patient. During the operation, we found yellow vessels, which were thought to be lymphatic vessels filled with a yellow solid substance, just beneath the superficial fascia at the left ankle. Pathological examination of the thrombi revealed hyaline material mixed with cell components. The cells were categorised as lymphatic endothelial cells, as they were positive for podoplanin. There was no evidence of malignancy. Causes of idiopathic lymphatic thrombus such as this may be one of the causes of so-called primary lymphoedema, and evaluation of such cases may be the first step towards elucidating the mechanisms involved in the development of primary lymphoedema.