MSK Flashcards
A 40-year-old male with long standing Rheumatoid arthritis has generalised lymphadenopathy increasing over the past 4 years, malabsorptive diarrhoea and a restrictive cardiomyopathy. Which of the following statements is most correct?
- The combination suggests superadded Sjogren’s Syndrome
- The combination suggest systemic amyloidosis and may be diagnosed by renal or mouth/rectal biopsy
- The patient should be screened for HIV infection
- The combination suggests a progression of a MALT lymphoma
- The combination suggests scleroderma, particularly if antibodies to the Fc fragment of immunoglobulin are present.
- *The combination suggest systemic amyloidosis and may be diagnosed by renal or mouth/rectal biopsy
Osteoporosis is least likely to be associated with (August 2016)
a. Hypoparathyroidism
b. Multiple myeloma if there are no lucent lesions
DDx for osteoporosis: o Idiopathic o Endocrine - Hypogondism (Ovarian – post menopausal; Testicular – eunuchoidism) - Cushing syndrome - Diabetes - Acromegaly - Addison’s disease - Hyperthyroidism - Mastocytosis - Pseudohypothyroidism - Pseudopseudohypothyroidism o Disuse - Pseudopermeative pattern o Iatrogenic - ie Steroid use; Heparin o Deficiency states - Vitamin D; Protein o Congenital - Osteogenesis imperfecta - Turner syndrome - Homocystinuria - Neuromuscular disease - Mucopolysaccharidoses - Trisomy 13 and 18 - Glycogen storage disease - Progeria
Multiple myeloma has two main patterns of diffuse disease
o Numerous, well circumscribed lytic bone lesions (more common)
o Generalised osteopaenia w vertebral compression fractures +/- vertebra plana
ANSWER: Hypoparathyroidism is least likely to be associated w osteoporosis, although pseudohypoparathyroidism & pseudopseudohypoparathyroidism are
Regarding Paget’s disease of the bone, which is false: (March 2015)
a. Polyostotic form leads to extramedullary haematopoesis
b. Rarely affects the fibula
c. Hearing loss is due to involvement of the external ear canal
d. Can get basilar invagination
e. Can get high output cardiac failure
Hearing loss in Paget’s disease can be sensorineural or conductive
o Sensorineural: Compression of the nerves from bone overgrowth or loss of bone mineral density in the cochlea
o Conductive: fixation of the middle ear ossicles
Complications of Pagets disease o Fractures o Nerve compression o OA o Skeletal deformities e.g. tibial bowing or skull enlargement o High output cardiac failure o Osteosarcoma transformation in 1%
ANSWER: Hearing loss in Paget’s disease is not due to involvement of the external ear canal
What is not a complication in Pagets disease? (September 2013)
a. High output cardiac failure
b. Low output cardiac failure
c. Cranial nerve palsy
d. Platybasia
e. Malignant transformation
ANSWER: Low output cardiac failure
Platybasia - flattening of the skull base. Usually asymptomatic unless assoc w basilar invagination (odontoid projects into foramen magnum)
What lesion is not epiphyseal? (August 2016)
a. Paget disease
b. Osteomyelitis
Pagets in the long bones:
o Lesions begin in the proximal or distal subchondral region & progress towards the diaphysis
- Lesions rarely begin in the diaphysis, however this happens uncommonly in the tibia
o Forms a sharp delineation at the border of the normal bone, forming a ‘blade of grass’ or ‘flame shaped’ pattern
o May develop incomplete horizontal insufficiency fractures
- Form on the convex side of the bone
- Progress to ‘banana’ fractures
- Contribute to abnormal lateral bowing of the femur or anterior bowing of the tibia
Osteomyelitis in the long bones:
o Location of infection relates to the vascular supply of the bone
o Infants <12 months:
- Some metaphyseal vessels perforate the physis & anastomose w epiphyseal vessels - Infections involve the metaphysis, epiphysis & joint - Complications from epiphyseal infections include slipped epiphyses & joint deformities
o Toddlers & older children:
- Blood vessels terminate in loops w/in the metaphysis. Sluggish blood flow in the loops - Develop osteomyelitis in the metaphyses
o Adults:
- Terminal metaphyseal & epiphyseal vessels anastomose across the physeal scar - Adult OM can involve the metaphysis, epiphysis or the joint (more commonly than in children)
o Infection is rarely located in the cortex, unless due to direct inoculation
ANSWER: Both lesions can be epiphyseal in location; OM is more likely to be epiphyseal in adults
What is the most common cause of osteomalacia? (September 2013)
a. Renal failure
b. Vitamin D deficiency
c. Low dietary intake of phosphate
d. Hypophosphataemia
Causes of osteomalacia:
o Vitamin D def from sunlight or diet
o Deficiency of vitamin D metabolism - CRF
o Chronic liver disease
- Disruption of the pathway at 25-hydroxy vitamin D in hepatocytes
- Biliary dysfunction causing decreased absorption
o Decreased absorption of vitamin D
- Malabsorption syndromes (e.g. Crohn disease)
- Partial gastrectomy
o Decreased deposition of calcium in bones
o Defects in phosphate metabolism
- Phosphate deficiency from drugs or malabsorption
- Familial hypophosphataemia
- Fanconi syndrome
ANSWER: Vitamin D deficiency (although renal failure is a common cause of vitamin D deficiency)
Osteonecrosis is least associated with: (August 2016)
a. Gaucher disease
b. Thalassaemia major
c. Subcapital femoral fracture
d. Sickle cell disease
e. Caisson disease
Causes of osteonecrosis (PLASTIC RAGS) o P: Pancreatitis, pregnancy o L: Lupus o A: Alcohol o S: Steroids o T: Trauma o I: Idiopathic, infection o C: Caisson disease, collagen vascular disease o R: Radiation, rheumatoid arthritis o A: Amyloid angiopathy o G: Gaucher disease o S: Sickle cell disease
Caisson disease: diving related decompression illness
o Arterial gas embolization secondary to pulmonary decompression barotrauma
o Decompression sickness (Caisson disease):
- Mild: arthralgia, skin marbling, small patchy haemorrhages, lymphatic obstruction
- Serious & life threatening: Affecting the brain, spinal cord, inner ear and/or lung
Complications: bone & spinal cord infarction
Gaucher disease: most common lysosomal storage disease in humans
o AR, multisystem disease
o Deficiency of glucocerebroside & beta-glucosidase activity
- Accumulation of glycolipid within the lysosomes of macrophages in the bone marrow, spleen and liver
Types: Type I (most common) • Dx later (mean 21 years) • Skeletal symptoms (bone pain, pathological fractures, osteonecrosis, bone crises) - Osteopaenia, osteonecrosis, pathological fractures - Endosteal scalloping - Erlenmeyer flask deformities - H-shaped vertebrae - Paranasal sinus obliteration • Hepatomegaly & splenomegaly • Haematological disturbances • CNS spared
Type II
• Evident by 6 months
• Progressive neurological deterioration, resulting in death by the age of 2
Type III
• Neurological complications presenting by late adolescence or in early childhood
ANSWER: Thalassaemia is not assoc w osteonecrosis
What is not associated with osteonecrosis? (September 2013)
a. MI
b. Chronic pancreatitis
c. Gaucher’s disease
d. Connective tissue diseases
e. Sickle cell disease
ANSWER: Myocardial infarction is not assoc w osteonecrosis
What is not associated with osteonecrosis? (September 2013)
a. Cirrhosis
b. Chronic pancreatitis
c. Gaucher’s disease
d. Connective tissue diseases
e. Sickle cell disease
ANSWER: Cirrhosis is not assoc w osteonecrosis
Which is most true of osteosarcoma? (August 2016, March 2017)
a. Parosteal osteosarcoma is a lower grade compared to periosteal
b. Better survival for surface compared to central osteosarcoma
c. Periosteal osteosarcoma classically has a cleft between the cortex and the lesion
d. Parosteal typically has a cartilage matrix
PERIPHERAL OSTEOSARCOMA Parosteal osteosarcoma o Usually low grade o Ages 20-30 o F>M o Most common in the posterior aspect of the distal femur
Periosteal osteosarcoma o Intermediate grade o Ages 18-20 o M>F o Most common in the tibial meta-diaphysis
High grade surface osteosarcoma o High grade o Ages 20-30 o M>F o Most commonly in the mid femur, distal femur & mid tibia
CENTRAL OSTEOSARCOMA
• Most central osteosarcomas are high grade
Conventional osteosarcoma
o Osteoblastic (50% of conventional)
o Chondroblastic (25% of conventional)
o Fibroblastic (25% of conventional)
o Other rare subtypes (<1% of conventional)
• Telangectatic osteosarcoma; Small cell osteosarcoma
o Round cell
o Short spindle cell
ANSWER: Parosteal osteosarcoma is a lower grade compared to periosteal osteosarcoma
Which lesion is diaphyseal in location? (August 2014)
a. Osteoblastoma
b. Chondromyxoid fibroma
c. Osteochondroma
d. Chondroblastoma
e. Non-ossifying fibroma
- Osteoblastoma: metaphyseal
- Chrondromyxoid fibroma: metaphyseal (60% in long bones). Rarely can extend to the epiphyseal line or the articular surface
- Osteochondroma: metaphyseal, exophytic & pointing away from the physis
- Chondroblastoma: epiphyseal, occasionally crosses the growth plate
- Non-ossifying fibroma: metadiaphyseal
ANSWER: Non-ossifying fibroma is the most correct answer, although this is considered metadiaphyseal
Which of the following presents as a painless mass? (March 2014)
a. Periosteal osteosarcoma
b. Parosteal osteosarcoma
c. High grade surface osteosarcoma
d. Telangectatic osteosarcoma
e. Small cell osteosarcoma
Clinical presentation of osteosarcoma subtypes:
o Periosteal osteosarcoma: painless or low grade pain
o Parosteal osteosarcoma: sometimes painless
o High grade surface osteosarcoma: very painful, may have pathological fracture
o Telangectatic osteosarcoma: very painful, may have pathological fracture
o Small cell osteosarcoma: painful
ANSWER: Periosteal osteosarcoma more commonly presents as a painless mass
Which is false regarding diaphyseal aclasia? (March 2016)
a. It is sporadic
Hereditary multiple exostoses (aka diaphyseal aclasia);
o AD condition w incomplete penetrance in females
o Characterised by the development of multiple osteochondromas
Clinical:
- Most diagnosed by age 5, almost all diagnosed by age 12
- Multiple large lesions may give significant joint deformity
Complications of lesions: - Vascular impingement - Neural impingement - Fractures - Bursitis - Deformity - Malignant transformation • More common than in sporadic cases
Associations with sarcomatous transformation (GLAD PAST): - Growth after skeletal maturity - Lucency (new) - Additional uptake on NM studies - Destruction of the cortex - Pain after puberty (and) - Soft tissue mass - Thickened cartilage cap (>1.5cm)
ANSWER: Diaphyseal aclasia is an autosomal dominant condition – not sporadic
Chondrosarcoma. Which is not true? (March 2015)
a. Clear cell chondrosarcoma occurs in the pelvis
b. Hyaline chondrosarcoma occurs in the rib
c. Mesenchymal chondrosarcoma occurs in the mandible
d. Myxoid chondrosarcoma occurs in soft tissues
e. Dedifferentiated chondrosarcoma occurs in recurrent tumour
• Malignant tumours which produce cartilage
Histological subclassifiaction (Robbins) o Conventional (hyaline cartilage producing) o Clear cell o Dedifferentiated o Mesenchymal variants
Epidemiology
o Typically 4th & 5th decades
- Younger patients for clear cell & mesenchymal variants
Location:
o Classically arises in the axial skeleton including pelvis, shoulders & ribs
o Clear cell is the exception – occurs in the epiphyses of tubular long bones
o 15% of chondrosarcomas are secondary, arising from pre-existing enchondromas or osteochondromas
Clear cell chondrosarcoma: o 3-5th decades o Epiphyses of long bones, 60% in the femur o Typically low grade o Mimics chondroblastoma on imaging
Hyaline chondrosarcoma/conventional chondrosarcoma:
o Most common subtype
o May be high, intermediate or low grade
o Locations:
- Long bones (45%) – femur most commonly
- Pelvis (25%)
- Ribs (8%)
- Spine (7%)
- Scapula, sternum, skull
o Low grade chondrosarc can mimic enchondroma on imaging
Mesenchymal chondrosarcoma:
o Rare subtype which can occur in the bone or soft tissues. Usually high grade lesions
o Younger patients
Location:
- Bone lesions: mandible & facial skeleton most common
- Soft tissue lesions have a predilection for the head & neck: meninges / brain, orbit, larynx, sinonasal cavity
• Also occur in the soft tissues of the thigh
Myxoid chondrosarcomas:
o Mesenchymal & myxoid chondrosarcomas account for the majority of soft tissue sarcomas
- Usually high grade
- Peak incidence of myxoid chondrosarcomas at age 50
Location:
- Typically involve the extremities, thigh most common
Dedifferentiated chondrosarcoma:
o Combined tumour made up of two components which are sharply demarcated
o Poor prognosis – 0-18% survival at 5 years. 90% will develop lung metastases
ANSWER: Clear cell chondrosarcoma does not occur in the pelvis – seen in the epiphyses of long bones
Which is false of chondroblastoma? (March 2016)
a. Arise in metaphysis
b. Can be associated with a periosteal reaction
Chondroblastoma:
o Benign cartilage tumour arising in the epiphysis of a skeletally immature patient
Location:
>75% in the long bones
Epiphyseal, may extend into the metaphysis
Proximal humerus most common
Characteristics: Geographic lytic lesion 30-50% contain chondroid matrix Majority have a sclerotic margin Eccentric w/in the epiphysis Smooth, thick periosteal reaction in longstanding lesions (50%)
Epidemiology:
10-25 years old
Male > female
o Treated with curettage and bone graft. Consider ablation in small lesions
DDx:
- Clear cell chondrosarcoma (may appear identical)
- Giant cell tumour (arises in metaphysis & extends to epiphysis, skeletally mature)
- Osteomyelitis (rare in epiphysis)
- LCH (rare in epiphysis)
ANSWER: Chondroblastoma typically arises in the epiphysis, but can extend into the metaphysis
Regarding fibrous dysplasia, which is true? (March 2015)
a. McCune Albright includes hypercortisolism
b. Polyostotic form without endocrine effects presents later than the monostotic form
c. Monostotic has more association with osteosarcoma
d. Monostotic form has an association with Café-au-lait spots
Fibrous dysplasia
o Benign, fibro-osseus lesions which can be monostotic or polyostotic
Polyostotic:
- GNAS mutations
- More commonly unilateral (esp McCune-Albright)
- 2/3 present before the age of 10
• Painful if assoc w microfractures, esp the femoral neck or tibia)
McCune-Albright syndrome: • Polyostotic, unilateral • More common in females Associations & presentations: o Coast of Maine Café-au-lait spots o Endocrine abnormalities: - Precocious puberty (Abnormal PV bleeding in 25%) - Hyperthyroidism - Diabetes - Hyperparathyroidism - Rickets - Acromegaly - Cushing’s syndrome – 7%
Mazabraud syndrome:
- Polyostotic fibrous dysplasia & multiple soft tissue myxomas
- Usually in the large muscle groups
- More frequently in women and presents in middle age
o Malignant transformation is very uncommon, but degeneration to osteosarcoma or fibrosarcoma has been reported
Craniofacial appearances of fibrous dysplasia:
Cherubism: symmetric involvement of the maxilla & mandible
- Leontiasis ossea: involvement of the facial & frontal bones, giving a ‘lion-like’ face (severe craniofacial osseous thickening)
- Cranial nerve palsies are assoc w craniofacial FD secondary to bony overgrowth of the foraminae & nerve compression
ANSWER: McCune-Albright includes hypercortisolism
Which is true regarding Ewing sarcoma? (September 2013)
a. Differential includes neuroblastoma
b. Differential includes aggressive chondrosarcoma
c. Arises from the metaphysis
d. Peak age is the third decade
Ewing sarcoma
o Second most common malignant tumour of childhood
o Arise from the medullary cavity
Epidemiology:
- Children and adolescents - Most common in the second decade - Slight male predilection
Clinical:
- Non-specific symptoms - Pathological fracture - ESR elevated
Pathology:
- Small round blue cell tumour (Ewing sarcoma family of tumours) - t(11;22)(q24;q12) rearrangement
Location (geography):
- Lower limb: 45% - Pelvis: 20% - Upper limb: 13% - Spine & ribs: 13% (Sacrococcygeal region most common) - Skull/face: 2%
Location (distribution): - Long bones: 50-60% • Mid-diaphysis – 33% • Metadiaphysis – 44% • Metaphysis – 15% • Epiphysis – 1-2% - Flat bones: 40%
ANSWER: Differential includes neuroblastoma (both small round blue cell tumours)
Regarding Ewing sarcoma, which is false? (March 2017)
a. Spreads to the lymph nodes before haematogenously
b. Is like a PNET elsewhere but more benign
ANSWER: Both statements are false. Spread of Ewing sarcoma is bones > lung > lymph nodes
