Hereditary progressive muscle weakness work-up

Screening tests

Serum electrolytes, calcium/phosphorus, magnesium, lactate, pyruvate, liver and thyroid function tests, blood gasses

Serum CK, aldolase, myoglobin

CBC, ESR

EMG, NCVs 

Spirometry (forced vital capacity)

ECG, Echocardiogram

Ischemic forearm testing

Specific investigations

Assays

Lymphocytic acid a-glucosidase (AMD), glycogen debrancher enzyme activity in WBC or muscle or liver biopsy specimens.

Genetic testing

DNA testing for dystrophin Xp21.2 gene deletion (from WBC or muscle tissue (50 mg)), fascioscapulohumeral 4q35 deletion, EDMD-XR gene mutation, oculopharyngeal MD14q deletion, DMPK gene for DM1, DM2 gene for PROMM, dysferlin gene (Miyoshi DMD)

Muscle biopsy: one specimen for hematoxylin & eosin, one specimen for histochemistry (fresh sample), one specimen for EM (in glutaraldehyde) and one specimen for biochemistry and genetics (fresh sample)

helpful for differential diagnosis between acid maltase and debrancher enzyme deficiency, hypokalemic polymyopathy, mitochondrial myopathy, carnitine myopathy, FSHMD, LGMD CCM, nemaline myopathy: should include in addition to specific histochemical stainings, hematoxylin & eosin, modified Gomori trichrome staining (CCM, nemaline myopathy), ATPase stain, NADH-trazolium reductase and staining for dystrophin protein (immunostaining and immunoblot, or ELISA).

Pharmacological trial

Prednisolone 6-month trial period.  

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