Parents of a toddler boy noticed he began to walk on his toes, was falling often

Question

Parents of a toddler boy noticed he began to walk on his toes, was falling often, and struggled to stand back up. Over time it became more difficult for him to life his knees high, which a±ected his ability to run. At age six, doctors noted that he had progressive muscle wasting. Over more time, his trunk muscles began to weaken along with the others, and as a result, he developed a protuberant abdomen.Lordosis becomes evident as well. He was con²ned to a wheelchair at age eight and he began to develop muscular contractures.

1. This toddler boy has an x-linked recessive disorder that results in progressive muscular weakness and muscle contractures. What is it called? What does it mean to be x-linked?

2. De²ne the term "dystrophy".Why is this term appropriate when describing the boy's case?

3. The boy in this case ²rst showed signs of his disorder when he began walking on his toes. What are ALL of the muscles that are used to walk on his toes? (Hint: there are many answers here).

4. Another common problem seen in patients with this disorder is lordosis and abdominal protuberance. What muscles would become weakened to cause abdominal protuberance? (Hint: there are many answers here too!).

Explanation / Answer

1- This hereditary X-linked recessive disease characterized by progressive muscular weakness is Duchenne-type muscular dystrophy. In humans there a two types of sex chromosomes X&Y which determine the sex of the human. Chromosomes are responsible for the transmission of the hereditary characterstics from one generation to next,X-linked means that if there is a mutation on the X gene it can result in the phenotype to be expressed in males or females who are homozygous. Being X-linked means that there is mutation in the gene that is located on X chromosome which is causing the disease.

2- Dystrophy means defective nourishment. In muscular dystrophy there is death to muscle and replacement by fat and connective tissue, with concomitant metabolic defects. This boy has Duchenne muscular dystrophy which is characterized by muscle weakness due to degenaration which is defined as dysrophy, and it has been observed in his case that he had progressive muscle wasting and is unable to walk.

3- Muscles involved in walking "on the toes" are the gastrocnemius and the soleus. The tibialis anterior muscles are "weakening" failing to pull the toes up (opposing the gastrocnemius muscles).

4- The abdominal muscles that weaken in certain cases of lordosis and abdominal protuberance are the following:

Lordosis: quadtratus lumborum and iliocostalis lumborum

Abdominal protubernace: external oblique, internal oblique, transversus abdominus, and rectus abdominus.

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