Summary: Glycogenosis type VII (Tarui’s disease) is resulted from the deficiency of the M-isoform of phosphofructokinase. Although there are three isoforms, the muscle contains only the M-isoform. It is transmitted in an autosomal recessive pattern and the gene for the M-isoform is on chromosome 1(cenàq23). There is a severe infantile form, a classic form that has childhood onset, and a form with late adulthood onset. Hemolysis is present in all forms. Histologically, the amount of glycogen storage is often modest. Polyglucosan bodies may be present. The absence of phophofuctose kinase can be demonstrated by histochemical technique.

Clinical features:

· Classic form: Onset is most often in childhood but some cases (including the original cases described by Tarui) may have onset at early adulthood (late second and third decade). There is exercise intolerance and initial presention is vague and often leading to delay in diagnosis for several years. Clinical symptoms may be similar to McArdle’s disease. Exercise induces muscle pain and stiffness. Usustained exercise mayt cause myoglobinuria, nausea, vomiting, and weakness. Exercise does not cause increase in serum lactate but increase in serum ammonia and inosine monophosphate and myogenic hyperuricemia. Symptoms may be similar to McArdle’s disease. This form is compatible with prolonged survival.

· Rare infantile form: This form has severe congenital weakness, respiratory difficult, and short survival. Contracture, corneal opacity and mental retardation have also been described in these cases.

· Rare adult from: These patients often do not have clear exercise intolerance by they develop fixed weakness in late adulhood.

Genetics: Autosomal recessive, often seen in Ashkenazi Jews. The gene for the M (muscle) isoform of phosphofructokinase is in chromosome 1(cenàq23). The P (platelet) isoform is on chromosome 10p and the H (hepatic) isoform is on chromosome 21q22.3.

HISTOPATHOLOGY AND IMMUNOHISTOCHEMISTRY: Head

Histochemistry:

· Glycogen: The glycogen tends to accumulate as subsarcolemmal cresents. Dissolution of glycogen during processing may lead to empty spaces. The glycogen storage material is PAS(+), and diastase sensitive in most cases although diastase resistant material that are positive for colloidal iron may also be seen in some adult cases.

· Polyglucosan body: Up to 10% of the fibers may contain polyglucosan bodies.

· Necrotic and regenerating fibers: Biopsy after myoglobinuria or sternous exercise may reveal necrotic and regenerating fibers.

· Phosphofructose kinase activity: The lack of enzymatic activity may be demonstrated by histochemical method.