Becker Muscular Dystrophy Clinical Presentation

  • Author: Benjamin R Mandac, MD; Chief Editor: Denise I Campagnolo, MD, MS   more...
 
Updated: Nov 28, 2011
 

History

A typical developmental history of a patient with BMD may include the following:

  • Delayed gross motor milestones (eg, late walking, running, jumping, difficulty with stair climbing) may be reported.
  • Initially, some children who are later diagnosed with BMD may be called clumsy.
  • Increasing numbers of falls, toe walking, and difficulty rising from the floor may be later features.
  • Proximal muscle weakness is reported.
  • Subclinical cases may manifest later in life; dilated cardiomyopathy can be the first sign of BMD.
  • Elbow contractures may be seen later in life.
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Physical

  • The Gower sign is not a specific finding for muscular dystrophy, but it does point to proximal weakness in the hip extensors, leading to the pattern of movement seen when patients rise from the floor.
  • A weakness pattern limited to specific muscle groups may help to differentiate BMD from other muscular dystrophies (such as limb-girdle and Emery-Dreifuss muscular dystrophies).
  • Progressive, symmetrical muscle weakness and atrophy with pseudohypertrophic calves may be seen.
  • Cases have been described of patients presenting without weakness but with symptoms of cardiomyopathy or cramps as the only indication of a myopathic process. Isolated weakness to the quadriceps femoris may be the only symptom noted.
  • Fasciculation or sensory modality abnormalities can exclude the diagnosis of a dystrophinopathy.
  • Preservation of neck flexor muscle strength may differentiate BMD from DMD.
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Causes

BMD is an X-linked, recessive, inherited disorder. A family history of similarly affected maternal uncles assists the clinician in confirming a diagnosis of BMD.

  • A woman is an obligate heterozygote if she has an affected son and one other affected relative in the maternal line.
  • A woman with more than 1 affected child and no family history in the maternal line may have a germline mutation or a germline mosaicism.
  • An isolated proband without a family history may be explained by a mutation occurring in the egg at or following conception in which only some cells were affected (mosaicism). On the other hand, the proband's mother may have inherited the gene mutation if (1) her mother was a carrier or (2) her mother or father had somatic or germline mosaicism.
  • Siblings of the proband are at risk of transmitting the gene defect based on the carrier status of the mother.
    • A carrier mother has a 50% transmission rate for the mutation, per pregnancy; daughters inheriting the mutation will be carriers, and sons with the mutation will be affected.
    • Mothers with germline and/or somatic mosaicism have a higher risk of transmitting the mutation.
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Contributor Information and Disclosures
Author

Benjamin R Mandac, MD  Chief of Physical Medicine and Rehabilitation, Medical Director of Pediatric Rehabilitation, Kaiser Permanente at Santa Clara

Benjamin R Mandac, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine and American Academy of Physical Medicine and Rehabilitation

Disclosure: Nothing to disclose.

Specialty Editor Board

Elizabeth A Moberg-Wolff, MD  Associate Professor, Department of Physical Medicine and Rehabilitation, Children's Hospital of Wisconsin, Medical College of Wisconsin

Elizabeth A Moberg-Wolff, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine and American Academy of Physical Medicine and Rehabilitation

Disclosure: Medtronic Neurological Grant/research funds Speaking and teaching

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Kat Kolaski, MD  Assistant Professor, Departments of Orthopedic Surgery and Pediatrics, Wake Forest University School of Medicine

Kat Kolaski, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine and American Academy of Physical Medicine and Rehabilitation

Disclosure: Nothing to disclose.

Kelly L Allen, MD  Medical Director, Medevals

Disclosure: Nothing to disclose.

Chief Editor

Denise I Campagnolo, MD, MS  Director of Multiple Sclerosis Clinical Research and Staff Physiatrist, Barrow Neurology Clinics, St Joseph's Hospital and Medical Center; Investigator for Barrow Neurology Clinics; Director, NARCOMS Project for Consortium of MS Centers

Denise I Campagnolo, MD, MS is a member of the following medical societies: Alpha Omega Alpha, American Association of Neuromuscular and Electrodiagnostic Medicine, American Paraplegia Society, Association of Academic Physiatrists, and Consortium of Multiple Sclerosis Centers

Disclosure: Teva Neuroscience Honoraria Speaking and teaching; Serono-Pfizer Honoraria Speaking and teaching; Genzyme Corporation Grant/research funds investigator; Biogen Idec Grant/research funds investigator; Genentech, Inc Grant/research funds investigator; Eli Lilly & Company Grant/research funds investigator; Novartis investigator; MSDx LLC Grant/research funds investigator; BioMS Technology Corp Grant/research funds investigator; Avanir Pharmaceuticals Grant/research funds investigator

References

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