A 9-year-old boy presented with difficulty in climbing stairs and combing. On examination, bilateral calves are swollen and the child uses his feet to stand up on his legs. What is the next diagnostic step?
Ans. a. Creatine kinase levels (Ref: Harrison 19/e p462e-6. 18/e p3490-3491)Symptoms of difficulty in climbing stairs and combing in a 9 years old boy, with swollen bilateral claves are highly suggestive of Duchenne muscular dystrophy (Pseudohypertrophic Muscular Dystrophy). Another evidence is that child uses his feet to stand up on his legs (Gower's sign). Next diagnostic step is creatine kinase levels."Duchenne Muscular Dystrophy: By age 5 years, muscle weakness is obvious by muscle testing On getting up from the floor, the patient uses his hands to climb up himself (Gower's maneuver). Contractures of the heel cords and iliotibial bands become apparent by age 6 years, when toe walking is associated with a lordotic posture. Loss of muscle strength is progressive, with predilection for proximal limb muscles and the neck flexors; leg involvement is more severe than arm involvement. "--Harrison 19/e p462e-6 "Creatine kinase (CK) is the preferred muscle enzyme to measure in the evaluation of myopathies. Damage to muscle causes the CK to leak from the muscle fiber to the serum. "''Serum CK levels are invariably elevated to between 20 and 100 times normal. The levels are abnormal at birth but decline late in the disease because of inactivity and loss of muscle mass. -- Harrison 19/e p462e-6Duchenne Muscular Dystrophy (Pseudohypertrophic Muscular Dystrophy)Duchenne muscular dystrophy is the MC hereditary neuromuscular disease affecting all races & ethnic groups.Inheritance: X-linked recessive; Abnormal gene lies on chromosome 21 (Xp21)QAge on onset: 2-5 yearsQ (Doesn't present at birth or during infancyQ)Pathogenesis:Caused by mutation in the gene responsible for producing dystrophinQDystrophin is subsarcolemmal protein localized to the inner surface of sarcotemma of the muscle fiber.Dystrophin is part of Dystrophin-Glycoprotein sarcolemmal complex and this protein deficiency leads to secondary loss of sarcoglycans & dystroglycans resulting in weakness of sarcolemma, causing membrane tears and muscle fiber necrosisQ.Clinical Features:Early development of child is normal, the disease begins to manifest when the child starts walkingQ.The child walks clumsily, has the difficulty in climbing stairs & the gait is waddlingQ.Hypertrophy of calf muscle is a characteristic sign & is visible by the age of 4-5 years, called pseudohypertrophyQ (not true hypertrophy because muscle is replaced by fat & connective tissue)Pelvic girdle involvement is very common and can be elicited by Gower's signQGower's sign: Patient using his arms to climb up the legs in attempting to get up from the floorQ.Hypertrophied MusclesAtrophied Muscles* Calf, Glutei & DeltoidQ* BrachioradiaiisQ* Tongue muscles* Sternal head of pectoralis majorQ* SupraspinatusQLoss of muscle strength is progressive; Proximal muscles & neck are involved moreQLeg involvement is more severe than arm involvementQContracture of heel cords & iliotibial hand occursQ (by age of 6 years)Eventually all muscles are atrophiedQComplications of Duchenne Muscular DystrophyChest DeformityCardiacIntellectual Impairment* Progressive scoliosisQ develops* Impairs pulmonary functionQ* By 16-18 years of age, patients are predisposed to serious fatal pulmonary infectionsQ.* Cardiomyopathy & CHF may be seenQ* Cardiac cause of death is uncommon* Intellectual impairment is common* Intelligence is usually subnormalDiagnosis:Elevation of creatinine phosphokinase (20-200 times)QEMG: Features of myopathyQMuscle BiopsyDefinitive diagnosis is established on the basis of dystrophin deficiency in biopsied muscle tissueQDiffuse changes of degeneration & muscle fibers of vary ing sizeQGroup of necrotic & regenerating muscle fibers are seenQTreatment:Significant alteration in the progression of disease has been seen with prednisoloneQ.Prognosis:Patients die in the second decade of life because of respiratory failure or due to associated cardiomyopathyQ.Age on onset* Before 5 yearsQConfined to wheel chair Inability to walk* After age 12 yearsQRespiratory failure* In 2nd or 3rd decade (After 16-18 yearsQ)
Creatine kinase levels
EMG
Nerve conduction velocity
RA factor
Peripheral Nerve & Muscles