Primary lymphedema occurs without any obvious cause, and is thought to be the result of an underdeveloped or inefficient lymph system. In some cases, it may be hereditary. Swelling may be present at birth of soon after - Lymphedema Congenita; can occur in before the age of 35 - Lymphedema Praecox; or develop after age 35 - Lymphedema Tarda. Primary lymphedema is more common in females and occurs more often in the lower extremities. remities.