Case: 6-year-old Boy with Weakness

by Roy Strowd, MD

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    00:01 So let's start with a case.

    00:03 A 6-year-old boy who presents with weakness.

    00:06 This 6-year-old boy presents for new evaluation of weakness and difficulty walking.

    00:11 The boy was born at 37 weeks by uncomplicated vaginal delivery.

    00:15 He met all milestones well until about 3 years ago or 3 years of age, when he first started having difficulties with walking, particularly running longer distances, where he would get tired and weak.

    00:29 Over the past several years, he has had progressive weakness with difficulty running, jumping and climbing.

    00:35 He has no other medical conditions.

    00:37 He's an only child and his mother is 42 years old, and has had an abnormal gait with arched back but no other signs of weakness.

    00:46 And she does see a cardiologist for an unspecified heart rhythm abnormality.

    00:53 Over the last 6 months, the boy's weakness has continued to worsen.

    00:57 He now has difficulty standing up from a lying position.

    01:00 His calf muscles are enlarged and hypertrophied bilaterally and symmetrically.

    01:05 He has no problems breathing.

    01:07 A neurologic examination shows proximal weakness in the arms and legs.

    01:11 Cranial nerves, sensory examination, reflex exam and cerebellar exam are all normal.

    01:18 Workup shows a markedly increased creatine kinase over 40,000 IU/mL.

    01:25 So what's the most likely diagnosis? Well, let's go back and look through some of the key details of this case.

    01:32 First, we see that this is a young child, which is tipping us off that this may be an inherited muscle disorder.

    01:39 And the patient presents with progressive weakness, which is really important when we differentiate the muscular dystrophies from other inherited causes of muscle disorders.

    01:49 On the second part of the case, we see a number of key findings.

    01:53 First is the distribution.

    01:55 This is proximal weakness, proximal in the legs and proximal in the arms.

    01:59 And that really puts us into the bucket the category of proximal predominant muscular dystrophies.

    02:06 What are the sensory findings? Well, here we see the sensory exam is normal.

    02:10 The reflex exam is also normal.

    02:12 And then there's a fourth important wildcard and that is calf muscle enlargement or hypertrophy or pseudohypertrophy, which will point us in the direction of a muscular dystrophy, that and we see this really elevated creatine kinase, which points us to some type of inflammation in and around the muscle.

    02:31 So what's the most likely diagnosis? Polymyositis, Duchenne's muscular dystrophy, Limb-girdle muscular dystrophy or Dermatomyositis? Well, polymyositis is an acquired cause of muscle disorder and this patient presents with an age, a sex and a distribution of weakness that is not consistent, inconsistent with polymyositis.

    02:54 Dermatomyositis presents with a rash in addition to acquired proximal muscle weakness, which is inconsistent with this case.

    03:02 Limb-girdle muscular dystrophy can be seen as a cause of muscular dystrophy but this patient's age and sex really points us to Duchenne's muscular dystrophy.

    About the Lecture

    The lecture Case: 6-year-old Boy with Weakness by Roy Strowd, MD is from the course Hereditary Neuromuscular Disorders.

    Included Quiz Questions

    1. Reflex examination
    2. Blood pressure determination
    3. Ability to balance on one foot
    4. Body weight and height measurement to calculate the body mass index
    5. Ability to walk heel-to-toe
    1. an inherited disorder.
    2. …has an autoimmune basis.
    3. …has elevated CK levels.
    4. …has a sudden onset.
    5. …usually has a rash.

    Author of lecture Case: 6-year-old Boy with Weakness

     Roy Strowd, MD

    Roy Strowd, MD

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