Phosphofructokinase (PFK) is an enzyme that is involved in the use and regulation of glucose as an energy source. Disruption of the PFKM gene can result in a Phosphofructokinase deficiency that leads to muscles that fatigue very easily, because they cannot use energy very efficiently. Affected dogs display muscle weakness, an inability to exercise properly, or muscle cramping. Characteristic of the disease is a brown discolouration of urine, caused by the excretion of the muscle breakdown product myoglobin in the urine.
There is no cure for PFK deficiency and treatment is supportive and to minimise long-term damage.