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What is Which of the following causes distal myopathy: and explain in detail?
Ans: A (Myotonic dystrophy) Ref: Harrison's Principles of Internal Medicine. 18th ed, pg 3499.3500Explanation (See the following table)Myotonic Dystrophy:Facial muscle (hatchet face), neck.palatal, pharyngeal, distal muscle of hands and feet weaknessFrontal baldnessMyotonia of thenar muscle, tongue, wrist extensorCardiac conduction defects, cataract, insulin resistanceMyotonia treated with phenytoin/mexilitineDrug induced proximal weaknessAmiodaroneChloroquineHCQColchicineLipid lowering drugsGlucocorticoidsZidovudineAlcoholAmphetamined-PenicillamincClofibratteVincristineEndocrine causes:Hypo/hyperthyroidismHyper/hypoparathyroidismCushing's syndromeOsteomalaciaRenal osteodystrophyAdrenal insufficiencyConn's syndromeAcromegalyDMChannelopathies:Malignant hyperthermia- Calcium channelHypokalemic periodic paralysis- Calcium & sodium channelHyperkalemic periodic paralysis- Sodium channelParamyotonia congenita-Sodium channelMyotonia congenita! (Thompson's disease)- Chloride channelAnderson-Tawil syndrome- Potassium channelMitochondrial myopathies: MERFF, MELAS.CPEO, MNGIE. Kearns-Sayre syndromeDisorders of carbohydrate & lipid metabolism: Me Ardle disease, CPT deficiency- In general, myopathies follow a proximal distribution of weakness and muscle wasting (with the notable exception of myotonic muscular dystrophy)- Neuropathies are generally distal in distribution (with the notable exception of juvenile spinal muscular atrophy