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244: MUSCULAR DYSTROPHY

Kay Tasso, PhD, PT, PCS

CONDITION/DISORDER SYNONYMS

  • Adult pseudohypertrophic muscular dystrophy

  • Becker muscular dystrophy

  • Benign X-linked recessive muscular dystrophy

  • Childhood pseudohypertrophic muscular dystrophy

  • Duchenne muscular dystrophy

ICD-9-CM CODES1

  • 359.0 Congenital hereditary muscular dystrophy

  • 359.1 Hereditary progressive muscular dystrophy

ICD-10-CM CODES2

  • G71.0 Muscular dystrophy

  • G71.2 Congenital myopathies

PREFERRED PRACTICE PATTERN3

  • 5E: Impaired Motor Function and Sensory Integrity Associated with Progressive Disorders of the Central Nervous System

PATIENT PRESENTATION

“A 3-year-old boy is brought to his pediatrician to be evaluated for difficulty walking and clumsiness. According to his parents, the patient began walking at the age of 18 months, but in the past year he has begun to fall more frequently and has difficulty getting up from the floor; often supporting himself with his hands along the length of his legs. Birth and developmental history until symptom onset are reportedly normal. There is no contributing family history.

On physical examination the young boy has significant muscle weakness of his hip flexors, knee extensors, deltoids, and biceps muscles. His calves are large, and he walks on his toes during ambulation. Laboratory studies reveal an elevated serum creatine kinase (CK) level of greater than 900 international units per liter (IU/L). Electromyography (EMG) of his muscles reveals a myopathy. Nerve conduction studies reveal relative normal nerve function.4

KEY FEATURES

Description

  • Group of genetic disorders that result in progressive muscle weakness due to loss of myofibrils5

  • Causes defects in muscle proteins: Weakens the musculoskeletal system

  • Muscle cell and tissue death

Essentials of Diagnosis

  • Nine major types of muscular dystrophy (MD)

  • Diagnosed through molecular characteristics

  • Diagnosis is dependent on

    • Age of patient at onset of symptoms

    • Areas of body involved

    • Rate of progression of symptoms

FIGURE 244-1

Summary of mechanisms involved in the causation of Duchenne muscular dystrophy (OMIM 310200). (From Murray RK, Bender D, Botham KM, et al. Harper’s Illustrated Biochemistry. 29th ed. www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)

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General Considerations

  • Duchenne MD (Type I)

    • Symptoms begin around 3 to 5 years of age

    • Characterized by pseudohypertrophy of calves

    • Progresses quickly

  • Becker MD (Type II)

    • Symptoms begin around 11 years of age

    • Characterized by muscle weakness of shoulder girdle, trunk, and extremities

    • Progresses slowly

  • Congenital MD5

    • Congenital MD with central nervous system disease (Fukuyama syndrome, Walker–Warburg syndrome, muscle–eye–brain disease)

    • Integrin-deficient congenital MD

    • Merosin-deficient congenital MD

    • Congenital MD with normal merosin

      • Symptoms begin at birth

      • Characterized by hypotonia and contractures at birth

      • Progresses slowly but varies

  • Congenital myotonic MD

    • Symptoms begin at birth

    • Characterized by severe hypotonia and muscle weakness at birth

    • Progresses slowly

      ...

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