Phosphofructokinase (PFK) deficiency is an inherited disease that affects both the field trial and show lines of English Springer Spaniels. M-PFK is an enzyme required for the metabolism of glucose into useable energy. Without the PFK enzyme, some cells, such as muscle cells and red blood cells, cannot produce adequate energy for their needs. Therefore, affected dogs display the following intermittent, clinical signs: weakness, lethargy, exercise intolerance, poor performance, muscle cramps, anemia, jaundice, and dark-colored urine. Dark-colored urine, a hallmark of this disorder, usually appears after strenuous exercise or after excessive barking, panting, and heat exposure. read more →