This paper presents a family case of brother and sister with unilateral lymphedema, set off spontaneously at prepuberty and earlier in the boy. They both developed a unilateral chylothorax at the age of 22-24. No congenital anomalies are present. The clinical and paraclinical data exclude forms of secondary lymphedema as well as the ones associated with gonadal dysgenesis. The family case history reveals that the parents are not kindred, appear healthy, without pulmonary complaints. Neither no other cases similar to the patients described nor other congenital anomalies or genetic diseases have been recorded in the family. The peculiarity of the cases consists in the fact that lymphedema is confined only to the left lower limb and that there are no modifications in the parents, suggesting an autosomal recessive transmission, which would be a pathogenic novelty. The association with chylothorax points to the importance of a thorough evaluation of the patient with lymphedema of the lower limb.