INTRODUCTION: Myoadenylate deaminase deficiency (MAD) constitutes the most common genetically determined enzymatic defect of the
skeletal muscle (2% of the
population ), however, it causes clinical symptoms such us
exercise -related
muscle cramps and
pain in quite a lower number of
patients , being exceptional in
children . CASE
REPORT A 7 year old boy is referred with intense myalgias after
physical exertion associating increased creatin
kinase level 3,273 UI/L (normal 24-195) which goes down in
rest period to increase again with myalgias during
exercise . The ischemic
forearm exercise test shows a flat
ammonia curve with a normal
lactate rise in relation to
control . In
muscle biopsy , an absence of the enzymatic activity of
myoadenylate deaminase is observed and the genetic analysis proves the 'nonsense' Q12X
mutation which he has in a homozygous status.
CONCLUSION: MAD deficiency must be ruled out in every
patient with exertional
myalgia and increased CK which normalizes when asymptomatic. The ischemic
forearm exercise test guides about the
muscle metabolic disorder type, although the definitive
diagnosis is obtained through the
muscle biopsy histoenzymatic analysis and
genetic techniques . Although rarely diagnosed in
children , MAD deficiency must be included in the
differential diagnosis of
syndromes with
exercise intolerance