Orthopedic Teaching Cases 2023, Jan, 17 | 12:00 am

Pediatric cases 21

CASE                               21                               

 

A 4-year-old male presents to your office as a self-referral by his mother. She is concerned that something is wrong with her little boy, as he does not seem to be reaching his motor milestones. She reports that he started walking at the age of 3, and currently has difficulty running and jumping along with his friends. On physical examination he is normocephalic, with normal appearing facies, and proportional arm and leg length. He has enlarged calf muscles and prominent lumbar lordosis. While the child is supine on the examination table, you ask him to stand up; he rolls to the prone position and uses his arms to progressively stand from a crawling position to standing.

The disorder that this child has is caused by a defect in the gene coding for what protein?

  1. Cartilage oligomeric matrix protein (COMP)

  2. Dystrophin

  3. Fibrillin

  4. Vitronectin

  5. Core-binding factor subunit alpha-1 (CBFA-1)

Discussion

The correct answer is (B). This patient has Duchenne’s muscular dystrophy (DMD) which most commonly presents in boys that are between 3 and 5 years old. They tend to gain motor milestones from 6 to 7 years old but often transition to a wheel chair secondary to proximal muscle weakness by age 12. Dystrophin helps to form a complex that mechanically links the sarcomere to the extracellular matrix. Remember to check creatinine kinase (CK) levels, which are often elevated between 10 and 200 times the normal reference levels. COMP is a protein that when mutated can result in pseudoachondroplasia or multiple epiphyseal dysplasia. Mutations in the gene encoding for fibrillin result in Marfan’s syndrome. Vitronectin is a protein involved in tumor metastasis due to its function in cell adhesion. CBFA-1 is encoded by the RUNX2 gene and its dysfunction results in cleidocranial dysplasia.

What is the inheritance pattern of patients with this disorder?

  1. Autosomal dominant

  2. Autosomal recessive

  3. X-linked dominant

  4. X-linked recessive

  5. Mitochondrial inheritance

 

Discussion

The correct answer is (D). Examples of autosomal dominant disorders include syndactyly, Marfan’s syndrome, achondroplasia, and Ehlers–Danlos syndrome. Examples of autosomal recessive disorders include diastrophic dysplasia, Friedreich’s ataxia, spinal muscle atrophy, and Gaucher’s disease. An example of an X-linked dominant disorder includes hypophosphatemic rickets. Myoclonic epilepsy and ragged-red fibers (MERRF) are examples of a disease with a mitochondrial inheritance pattern.

As part of your general work-up for patients with DMD you tell the mother that you plan to get a standing scoliosis radiograph in clinic which is displayed in Figure 10–39. You relay to the mother that his radiograph shows no sign of scoliosis, however his mother is deeply concerned about the possible development of scoliosis in the future.

 

 

Figure 10–39

 

If left untreated and once the patient is weak enough to need a wheelchair, you tell the mother that the chance of progression of scoliosis is:

  1. 10%

  2. 30%

  3. 50%

  4. 70%

  5. 90%

Discussion

The correct answer is (E). Patients with DMD become wheelchair bound secondary to progressive muscle weakness. This muscle weakness also involves the paraspinal muscles which leads to a lack of trunk control. If left untreated, this results in progressive scoliosis in almost all patients.

Relieved that she finally has a diagnosis, his mother asks about the best treatment options available to improve her son’s overall prognosis in regards to muscle weakness and progression of his scoliosis.

What is the best treatment that can be offered to patients with DMD which improves overall prognosis?

  1. Early posterior spinal fusion for Cobb angles >20 degrees

  2. Corticosteroid treatment starting before the age of 5

  3. Physical therapy focused on gait training and strengthening

  4. Methotrexate treatment

  5. Recombinant dystrophin injections before the age of 5

 

Discussion

The correct answer is (B) Glucocorticoid treatment starting before the age of 5. Corticosteroids should be offered to all patients with DMD. Treatment helps to prolong walking, transiently increases muscle strength, reduces falls, improves pulmonary function and cardiac function, and slows the progression of scoliosis. Its effect on scoliosis is quite profound; a recent study by Lebel et al. compared boys with DMD who were treated with glucocorticoids to boys with DMD who were not treated with steroids; both were walking prior to treatment. They found that 20% of boys in the treatment group developed scoliosis while 92% in the untreated group developed scoliosis. The general rule before steroid use became prevalent was to perform a posterior spinal fusion on patients with DMD who had 20-degree curves because of the rapid progression. The literature does not show that physical therapy, methotrexate, or recombinant dystrophin affect overall prognosis of DMD.

 

Objectives: Did you learn...?

 

 

The inheritance pattern of DMD and other common musculoskeletal disorders? The importance of obtaining scoliosis films of patients with DMD?

 

The rate of progression of scoliosis in patients with DMD who go untreated?

 

The importance of corticosteroids in slowing the progression of pulmonary,

cardiac, and spine dysfunction in patients with DMD?