In a patient, muscle cramps on exercise, +ve myoglobtalinemia, the disorder is –

McArdle's disease This is due to deficiency of muscle phosphorylase. Lack of this enzyme limits muscle ATP generation by glycogenolysis results in glycogen occ Clinical manifestations - Develop in late childhood or adult Exercise intolerance with a muscle cramp It is important to note that two types of activity tend to cause symptoms; i) The brief exercise of great intensity such as sprinting ii) Less intense but sustained activity, such as climbing stairs or walking uphill. Moderate exercise, such as walking on level ground, can be performed by most patients for long periods. Many patients experience a characteristic "Second wind" phenomenon If they slow down briefly at the 1st appearance of muscle pain, they can resume exercise with more ease. There may be exercise-induced myoglobinuria secondary to rhabdomyolysis. This can lead to acute renal failure. Serum creatine kinase is elevated.