Pediatric orthopedic cases 31

CASE                               31                               

 

A 13-year-old girl presents to your office, having just moved to your area in recent months. Her parent reports that she and other family members were followed by an Orthopaedic surgeon where they lived previously. She has never had any surgery. She reports some medial-sided knee pain with activity—both proximal and distal to the joint. No pain at rest. No constitutional symptoms. Her x-ray is shown (Fig. 10–51).

 

 

Figure 10–51

 

Mutations in which gene are associated with this disorder?

1. RUNX2

2. EXT2

3. COMP

4. FGFR3

5. FMR1

 

Discussion

The correct answer is (B). The RUNX2 gene encodes runt-related transcription factor 2 (also known as core-binding factor subunit alpha-1 [cbfa-1]). This is associated with osteoblast differentiation. Mutations in RUNX2 are associated with cleidocranial dysplasia. Disorders of the COMP gene (“cartilage oligomeric matrix protein”) are associated with pseudoachondroplasia. FGFR3 is the gene associated with achondroplasia. FMR1 is the gene mutation associated with Fragile X syndrome. Mutations in EXT 1 and EXT2 are associated with multiple hereditary

exostosis, the condition depicted above (Fig. 10–51).

 

Which of the following has the same inheritance pattern as this condition?

1. Rett syndrome

2. Limb-girdle muscular dystrophy

3. Charcot–Marie–Tooth

4. Sickle cell disease

5. Friedreich’s ataxia

 

Discussion

The correct answer is (C). Rett syndrome is a sex-linked dominant condition. Limb-girdle muscular dystrophy is autosomal recessive. Charcot–Marie–Tooth is autosomal dominant, the same as multiple hereditary exostosis. Sickle cell and Friedreich’s ataxia are autosomal recessive.

What should you tell the family about the overall risk of malignant transformation?

1. There is no risk of malignant transformation

2. 1% to 25%

3. 26% to 50%

4. 51% to 75%

5. Over 75%

 

Discussion

The correct answer is (B). Patients with MHE do have a risk of malignant transformation. The percent of those that go on to have malignant transformation is not clear but is thought to be in the range of 1% to 25%. Patients without MHE who have just a solitary osteochondromas have a less than 1% risk of malignant transformation.

Should any of the patient’s lesions undergo malignant transformation, which location is most likely, and to what lesion type will it most likely transform?

1. Distal femur, osteosarcoma

2. Distal femur, chondrosarcoma

3. Proximal humerus, osteosarcoma

4. Pelvis, chondrosarcoma

5. Pelvis, osteosarcoma

Discussion

The correct answer is (D). When there is malignant transformation of osteochondromas, they transform most commonly to chondrosarcoma. Lesions in the pelvis are more likely than peripheral lesions to have malignant degeneration.

What is the most common ankle deformity that you need to monitor for in patients with MHE?

1. Varus

2. Valgus

3. Equinus

4. Recurvatum

 

Discussion

The correct answer is (B). About half of patients with MHE develop ankle valgus. Depending on the severity of the deformity and growth remaining, sometimes excision of exostosis is all that is needed, but other times the addition of a medial hemiepiphysiodesis is needed to correct the deformity. The other deformities listed are not the most common deformity seen in patients with MHE.

 

Objectives: Did you learn...?

 

Multiple hereditary exostosis is an autosomal dominant disorder?

 

Mutations in the EXT family of tumor suppressor genes are found in the majority of patients with MHE?

 

Risk of malignant transformation for both solitary osteochondromas and in patients with MHE?

 

Important of monitoring for ankle valgus in patients with MHE?