Question 1

Osteoid osteoma is a small benign bone tumor associated with pain that is disproportionate to the size of the lesion. This pain is caused by an excess of which of the following substances? A) Interleukin (IL)-1 and IL-6 B) Leukotrienes C) Prostaglandin E₂ D) Complement C₃ E) Bradykinin

Accepted Answer

It has been known for many years that the severe pain caused by osteoid osteoma can be treated with aspirin. It has been shown that the pain is caused by prostaglandin E₂, which is produced by the proliferating osteoblasts in the tumor.

Question 2

Loss of heterozygosity, structural rearrangements, or point mutations of the retinoblastoma tumor suppressor gene (RB) are found in 60%-70% of all sporadic bone tumors. Which of the following is the best classification for this tumor?

A) Osteosarcoma
B) Osteoblastoma
C) Osteoid osteoma
D) Chondrosarcoma
E) Ewing sarcoma

Osteosarcoma

Accepted Answer

Changes involving the retinoblastoma tumor suppressor gene RB are found in 60%-70% of all sporadic osteosarcomas.

Question 3

The autosomal dominant bone disorder caused by a mutation of fibroblast growth factor receptor 3 (FGFR3) is characterized by short stature, rhizomelic shortening of limbs, frontal bossing of the skull, and midface abnormalities. Which of the following disorders is described by these characteristics?

A) Achondrogenesis
B) Achondroplasia
C) Multiple epiphyseal dysplasia
D) Synpolydactyly
E) Holt-Oram syndrome

Achondroplasia

Accepted Answer

Dwarfism, characterized by short limbs and relatively large head with midfacial changes involving the nose, is related to the mutation of the fibroblast growth factor receptor 3 (FGFR3) and is called achondroplasia.

Question 4

Compression fractures of vertebral bodies seen in elderly women are causally related to reduced recruitment of osteoclasts. This process is associated with an increased concentration of which chemical mediators in the bone?  &#10;A) Prostaglandins&#10;B) Leukotrienes&#10;C) Cytokines such as interleukin (IL)-1 and IL-6&#10;D) Oncogenes such as c-MYC and K-RAS&#10;E) Fibroblast growth factors

Accepted Answer

Compression fractures of vertebral bones in postmenopausal women are related to reduced levels of estrogens. Reduced levels of estrogen lead to an increase of cytokines, such as interleukin (IL)-1 and IL-6, which retard the recruitment of monocytes to the bones and inhibit their transformation into osteoclasts (a process known as osteoclast recruitment).

Question 5

Trinucleotide CTG repeat expansion plays a role in the pathogenesis of which of the following muscle diseases?&#10;A) Duchenne muscular dystrophy&#10;B) Becker muscular dystrophy&#10;C) Autosomal dominant limb girdle muscular dystrophy&#10;D) Autosomal recessive limb girdle muscular dystrophy&#10;E) Myotonic dystrophy

Accepted Answer

The trinucleotide CTG repeat expansion on chromosome 19q13.2-13.3 affecting the dystrophia myotonia-protein kinase gene is the genetic basis of myotonic dystrophy.

Question 6

A 20-year-old man is being treated for a soft tissue tumor of the lower extremity. The tumor is composed of malignant spindle-shaped cells and epithelial cells that form gland-like structures. Which of the following is the most likely diagnosis?

A) Leiomyosarcoma
B) Malignant fibrous histiocytoma
C) Primitive neuroectodermal tumor
D) Synovial sarcoma
E) Rhabdomyosarcoma

Accepted Answer

Synovial sarcoma is a biphasic soft tissue sarcoma composed of spindle cells and epithelial glandular-like cells.

Question 7

The primitive neuroectodermal tumor (PNET) of soft tissues has the same histologic features and the same chromosomal translocation as which of the following bone tumors?&#10;A) Osteosarcoma&#10;B) Chondrosarcoma&#10;C) Ewing sarcoma&#10;D) Malignant fibrous histiocytoma&#10;E) Giant cell tumor of bones

Accepted Answer

The primitive neuroectodermal tumor (PNET) is a soft tissue equivalent of Ewing sarcoma. These two tumors resemble one another histologically and have the same chromosomal changes.

Question 8

Which of the following muscle diseases is classified as an ion channel myopathy (channelopathy)?&#10;A) Dysferlin deficiency&#10;B) Becker muscular dystrophy&#10;C) Malignant hyperpyrexia&#10;D) Central core disease&#10;E) Myotubular myopathy

Accepted Answer

Malignant hyperpyrexia (malignant hyperthermia) is characterized by a hypermetabolic state (tachycardia, tachypnea, muscle spasm, and high fever) that is triggered by induction of anesthesia. Several mutations have been identified in these patients, including an L-type voltage-dependent calcium channel. Hence, this disease is classified as a channelopathy.

Deck 20: Bones, Joints, and Soft Tissue Tumors