title: A study of acute muscle dysfunction with particular reference to dengue myopathy.
abstract: BACKGROUND
  Acute myopathy is a common cause of acute motor quadriparesis which has various etiologies with different courses of illness and prognosis depending on the cause. Understanding this diversity helps us in proper approach toward diagnosis, predicting the prognosis, and possible complications and in improving the treatments that are being provided. This study was planned to study the clinical, electrophysiological, and etiological profile of patients presenting with acute myopathy. We also studied how dengue-related acute myopathy differs from other causes and also difference between myopathy due to myositis and hypokalemia in cases of dengue.
  
  
  METHODS
  This was a prospective, observational study involving all clinically suspected cases of acute myopathy of not more than 4 weeks duration with raised serum creatine kinase (CK) level. They were subjected to detailed clinical evaluation along with hematological, biochemical, microbiological, and electrophysiological studies and followed-up for outcome at 1 and 3 months. Muscle biopsy and histopathological examination were done in selected patients after taking informed consent. Statistical analysis was performed by appropriate methods using SPSS version 16.0 (Chicago, IL, USA).
  
  
  RESULTS
  We evaluated thirty patients of acute myopathy with raised CK level. Seventeen patients had fever, 11 had myalgia, and 5 had skin lesions. All presented with symmetric weakness, 17 (56.7%) patients having predominantly proximal weakness, neck or truncal weakness in 6 (20%), hyporeflexia in 12 (40%), with mean Medical Research Council (MRC) sum score of 46.67 ± 6.0. Eight (mean modified Barthel index [MBI] at presentation - 15 ± 3.7) patients had poor functional status according to MBI and 15 according to modified Rankin scale (MRS) (mean MRS score - 2.5 ± 1.2). Etiology was dengue viral infection in 14 patients; hypokalemia due to various causes other than dengue in 8; pyomyositis in 3; dermatomyositis, polymyositis, thyrotoxicosis, systemic lupus erythematosus, and unknown etiology in one each. Only eight patients had abnormal electrophysiology and seven among nine biopsies done were abnormal. At 1 month, 24 (80.0%) and 23 (76.7%) patients had achieved normal MBI and MRS scores with 28 (93.3) and 27 (90%) patients, respectively, at 3 months. Dengue with hypokalemia had less myalgia, more of hyporeflexia, and lower serum CK compared to those without hypokalemia.
  
  
  CONCLUSIONS
  Dengue infection and hypokalemia due to various causes are the most common causes of acute myopathy and are associated with rapid and complete recovery within 1 month. Shorter duration of illness, higher MRC sum score, better disability status at presentation, lower serum CK correlate with better outcome. Biopsy was decisive in <20% cases; hence, it is not primary investigation in acute myopathy.
authors.affiliation: Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Rajesh
authors.initials: R
authors.lastname: Verma
authors.affiliation: Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Vikram V
authors.initials: VV
authors.lastname: Holla
authors.affiliation: Department of Plastic Surgery, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Vijay
authors.initials: V
authors.lastname: Kumar
authors.affiliation: Department of Microbiology, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Amita
authors.initials: A
authors.lastname: Jain
authors.affiliation: Department of Pathology, Ram Manohar Lohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.
authors.forename: Nuzhat
authors.initials: N
authors.lastname: Husain
authors.affiliation: Department of Pathology, Ram Manohar Lohia Institute of Medical Sciences, Lucknow, Uttar Pradesh, India.
authors.forename: Kiran Preet
authors.initials: KP
authors.lastname: Malhotra
authors.affiliation: Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Ravindra Kumar
authors.initials: RK
authors.lastname: Garg
authors.affiliation: Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Hardeep Singh
authors.initials: HS
authors.lastname: Malhotra
authors.affiliation: Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Praveen Kumar
authors.initials: PK
authors.lastname: Sharma
authors.affiliation: Department of Neurology, King George Medical University, Lucknow, Uttar Pradesh, India.
authors.forename: Neeraj
authors.initials: N
authors.lastname: Kumar
keywords: Acute myopathy; dengue myositis; electrophysiology; muscle histopathology