A 9 yr old girl has difficulty in combing hairs and climbing upstairs since 6 months. She has gower's sign positive and maculopapular rash over metacarphalangeal joints. What should be the next appropriate investigation to be done ?
Ans. is 'c' i.e., Creatine kinase Difficulty in combing hairs and climbing upstairs suggests proximal muscle weakness.Presence of proximal muscle weakness along with maculopapular rash suggests dermatomyositis.Dermatomyositis is an inflammatory myopathy.Inflammatory myopathyThe inflammatory myopathy represents the largest group of acquired and potentially treatable causes of skeletal muscle weakness.They are classified into three major groupsPolymyositisDermatomyositisInclusion body myositis (IBM)Characteristic features of inflammatory myopathyProgressive and symmetric muscle weaknessExcept,IBM, which can have an asymmetric pattern early involvement of proximal musclesPatients usually report increasing difficulty with everyday tasks requiring the use of proximal muscles, such as getting up from a chair, climbing steps, stepping on to a curb, lifting objects or combing hair.Fine motor movements which depend on the strength of distal muscles such as buttoning a shirt, sewing, knitting, or writing are affected only late in the course of PM and DM.RememberThe distal muscles are involved fairly early in inclusion body myositis. Another important clinical feature of IBM is frequent falling which occurs due to early involvement of quadriceps in IBM.Sparing of ocular musclesOcular muscles are spared even in advanced untreated cases, if these muscles are affected the diagnosis of inflammatory myopathy should be questioned.Sparing of fascial musclesFacial muscles are unaffected in DM and PM.ButMild facial involvement can occur in IBM.Involvement of pharyngeal and neck Flexor musclesIn all forms of inflammatory myopathy, pharyngeal and neck flexor muscles are often involved causing dysphagia or difficulty in holding up the headTendon reflexesTendon reflexus are preserved ButMay be absent in severely weak or atrophied muscle especially in Inclusion body myositis.Intact sensationsSensations are intact in all types of inflammatory myopathy.Progression of the weaknessWeakness in PM and DM progresses sub acutely over a period of weeks or months and rarely acutely.By contrastWeakness progresses very slowly in IBM.More on inflammatory myopathy earlier it was believed that,If the muscular weakness is accompanied by skin rash it is called dermatomyositis where as if it remains confined to muscles only it is called polymyositis.Now daysPolymyositis is diagnosis of exclusionIt is a subacute myopathy affecting adults and rarely children who do not have the followingRashInvolvement of extraocular and facial muscles.Family history of neuromuscular disease - History of exposure to myotoxic drugs or toxins Endocrinopathy, neurogenic disease, muscular dystrophy, biochemical muscle disorder.Diagnosis of inflammatory myopathy * The diagnosis of inflammatory myopathy is confirmed by -Examining the serum muscle enzymesEMG findingsMuscle biopsySerum muscle enzymesThe most sensitive enzyme is the serum creatine kinase which in active disease can be elevated as much as 50 foldEMGEMG shows myopathic potentials, characterized by, short duration, low amplitude, polyphasic units on voluntary activation and increased spontaneous activity with fibrillations. These EMG findings are not diagnostic of an inflammatory myopathy but are useful to identify the presence of active or chronic myopathy.Muscle biopsyMuscle biopsy is the definitive diagnostic test for establishing the presence of inflammatory myopathy Muscle biopsy of polymyositis demonstratesScattered inflammatory foci with lymphocyte invading or surrounding muscle fibre (There is lack of chronic myopathic features such as increased connective tissue, atrophic or hypertrophic fibres).Muscle biopsy of Dermatomyositis demonstratesAtrophy of the fibres at the periphery of fascicleMuscle biopsy of inclusion body myositis demonstratesVirtually diagnostic features of IBM, which are intracytoplasmic subsarcolemmal vacuoles and eosinophilic inclusions in both the cytoplasm and nuclei of degenerating muscle fibres. The vacuoles contain and are rimmed by basophilic granular material.
ESR
RA factor
Creatine kinase
Electromyography
ALS and Other Motor Neuron Diseases