Leg ulcers may be caused by many different diseases. Most frequently, they are due to vasculopathies, to a lesser extent to metabolic, neuropathic or hematologic diseases. Neoplasms, connective tissue diseases, infections, trauma, and panniculitis should also be included in the differential diagnosis. A 38-year-old Caucasian female patient with hereditary prolidase deficiency developed progressive and very painful leg ulcers. The ulcers first appeared in childhood and did not respond to various treatments. Additional features of prolidase deficiency included mental retardation, short stature, extensive dental caries, and multiple malar teleangiectases. Hereditary prolidase deficiency is a very rare autosomal recessive disease. It is caused by heterogeneous mutations of the prolidase gene and affects many aspects of protein metabolism. Ion exchange chromatography and high voltage electrophoresis of urine can prove the suspected diagnosis. So far, there is no efficient therapy for hereditary prolidase deficiency. All reported treatment attempts have ended in failure.