Diagnosis of Myopathies Using Histology, Histochemistry, Immunohistochemistry and Electron Microscopy: A Single Center Experience

Background: Skeletal muscle biopsy is important for the diagnosis of motor unit disorders, systemic diseases and metabolic disorders. In some cases, routine histopathologic methods are not conclusive and histochemistry, immunohistochemistry and even an electron microscopic study are required. In this study, we describe our experience in the diagnosis of myopathies, considering all of the above-mentioned methods. Methods: During a period of 18 months, 43 specimens of patients with the impression of myopathy were submitted to the Pathology Department and were evaluated with H & E and histochemical stainings (PAS, Oil red O, ATPase, NADH-TR, Gomori Trichrome), immunohistochemistry (IHC) for dystrophin and electron microscopy. Three specimens were excluded from the study because there were only adipose tissues and no adequate muscle was present for evaluation. Results: Twenty three (57.5%) males and 17 (42.5%) females with a mean age of 34 years were evaluated. The results were as follows: Becker's muscular dystrophy (5 cases, 12.5%), Duchenne's muscular dystrophy (3 cases,7.5%), fascioscapulohumeral dystrophy (3 cases, 7.5%), limb girdle dystrophy (2 cases, 5%), polymyositis (6 cases, 15%), dermatomyositis (2 cases 5%), McArdle's disease (1 case, 2.5%), hypothyroidism myopathy (1 case, 2.5%), type 2 atrophy secondary to drugs and systemic diseases (2 cases 12.5%), congenital myopathy (2 cases 5%), McArdle (1 case 2.5%), unclassified myopathy (2 cases, 5%), and normal muscle biopsy (8 cases, 20%). Although a genetic study was not available to confirm the diagnosis of cases such as fascioscapulohumeral myopathy, the diagnosis was made after putting all of the findings together including clinical presentation, family history, NCV, EMG, etc. Conclusion: In the cases with no definite diagnosis by the histology, histochemistry and IHC, we should perform an EM study to find out the distinct ultra-structural changes which can be diagnostic for some muscle disorders. EM study in conjunction with light microscopy of muscle biopsy could be very helpful in establishing the diagnosis of some types of myopathies.