Volume 1, Number 1, April 2009, pages 56-57
doi:10.4021/jocmr2009.04.1231                                                                                       

Title

Chronic Non-Exertional Myalgia and Myoadenylate Deaminase Deficiency: a Possible Association

Aiesha Ahmed^{a, b}, Max R Lowden^a

^aPenn State College of Medicine, Hershey Medical Center, Department of Neurology - EC037, 30 Hope Drive, Hershey, PA 17033, USA
^bCorresponding author: E-mail: aahmed1@hmc.psu.edu

Manuscript accepted for publication April 7, 2009

Short title: Myoadenylate Deaminase Deficiency

       Myoadenylate deaminase deficiency is noted in skeletal muscles. It generally presents with exertional myalgias, fatigue and weakness. We present a patient who complained of constant pain unrelated to activity with biopsy finding consistent of myoadenylate deaminase deficiency.

Key words: Myoadenylate deaminase deficiency; Myalgia; Pain

        Myoadenylate deaminase catalyses the deamination of adenosine monophosphate to inosine monophosphate to release energy during muscle activity [1]. Myoadenylate deaminase deficiency is noted in skeletal muscles of 2-3% of patients with neuromuscular disorders [2]. Different isoforms are present in skeletal and smooth muscles, nerve bundles as well as in endothelial cells [3]. Clinical presentation is usually exertional myalgia and fatigue. We report a patient with biopsy proven myoadenylate deaminase deficiency which did not present with the usual exertion related muscle pain.

Case report

        A 46-year-old white man presented to the neuromuscular clinic with generalized muscle pain, fatigue and cramps for 10-15 years.  The muscle pain was described as constant, dull and achy. It was present during rest and was unchanged by exercise. There were no paresthesias, fever, swollen joints, rashes, or dark urine but the patient did admit to generalized weakness.

        The patient had a past medical history of spontaneous pneumothoraces and hypercholesterolemia. Family history reveals no neuromuscular diseases. Interventions including physical therapy, aquatherapy, tizanidine, tricyclic antidepressants, and nonsteroidal anti-inflammatory drugs provided minimal relief.

        On physical examination, he had intact muscle bulk, strength and tone throughout. His muscle stretch reflexes were normal. The remainder of the neurological examination was normal. Evaluations including blood work for connective tissue disorders, chemistry, thyroid studies, creatine phosphokinase and electrodiagnostic studies which failed to identify an etiology for his complaints.

Figure 1. Hematoxylin and eosin stain of muscle showing mild variation in myofiber size and shape but overall preservation of normal morphology as typically seen in myoadenylate deaminase deficiency. x 400.

Figure 2.  Adenosine monophosphate deaminase stain of muscle showing normal control (a) and markedly diminished myoadenylate deaminase activity (b). x 400.

        Exertional myalgia is seen with myoadenylate deaminase deficiency in most of the reported cases [4-7], along with fatigue and weakness. We present a case of longstanding constant pain which was not triggered by exertion. We found a few reports of resting pain in patients with myoadenylate deaminase deficiency, however these patients developed it either subsequent to having exertional mylagia for some time [3] or the pain was minimal at rest and would worsen on exertion [8].

      The authors declare no commercial associations or conflict of interest related to this article.

Lally EV, Friedman JH, Kaplan SR. Progressive myalgias and polyarthralgias in a patient with myoadenylate deaminase deficiency. Arthritis Rheum 1985;28:1298-1302.
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