Phosphoglycerate kinase deficiency
Overview
Phosphoglycerate kinase deficiency is a hereditary metabolic muscle disease. There are two distinct syndromes. There is a pure muscle syndrome characterized by recurrent cramps and muscle breakdown in response to intense exercise, and a "muscle plus" syndrome which may feature mental retardation and/or haemolytic anaemia. Phosphoglycerate kinase is a complex enzyme. Several subtypes of phosphoglycerate kinase deficiency have been identified,1 based on the tissues in which the enzyme deficiency occurs, and the type of inheritance.
Symptoms
* The most common features are enlarged liver, growth retardation, mild delay in motor development and elevated blood lipids. * There may be splenomegaly. * All of the symptoms usually improve as the child ages, and most adults are of normal height.
Prevention
Identification of the gene6 may permit prenatal diagnosis with a view to termination of pregnancy.
Diagnosis
It may resemble other types of glycogen storage diseases. There are a number of enzyme defects that can cause myoglobinuria3 as well as other causes: * Hypokalaemia, hypophosphataemia, myopathies, Acetyl-CoA dehydrogenase deficiency, and lactate dehydrogenase deficiency * Polymyositis and dermatomyositis * Malignant hyperthermia * Neuroleptic malignant syndrome * Crush syndrome * Muscle ischaemia secondary to arterial occlusion or insufficiency * Septicaemia * Drug abuse
Prognosis
Severity varies, but myopathic syndrome is usually slowly progressive. In one study of a large family many sufferers died before reaching adulthood