Chapter 130 - Pediatric Musculoskeletal Disorders and Syndromes

Question 1

Marfan’s Syndrome genetics

Answer 1

Autosomal DOMINANT (25% new mutations)
Fibrillin 1 defect (FBN1)
Chromosome 15q21

Question 2

Marfan’s syndrome phenotype

Answer 2

• tall, wingspan: height >1.05
• dolichostenomelia (tall and thin, long limbs)
• arachnodactyly and joint hypermobility

Cardiac Defects: GET A CARDS CONSULT AND ECHO
- aortic root dilatation -> aortic dissection
- mitral valve prolapse

Scoliosis: difficult to brace
- dural ectasia (dilation of the dura - scalloped vertebral bodies and nerve root herniation)
- GET AN MRI

SUPERIOR lens dislocation, myopia

Acetabular protrusio, severe pes planovalgus

Question 3

Ehler’s Danlos genetics

Answer 3

Classic form:
Autosomal DOMINANT
Col5A1, Col5A2 mutations

Type VI:
Autosomal RECESSIVE
lysyl hydroxylase mutation - key for collagen crosslinking
***severe kyphoscoliosis, globe rupture

Type IV: (vascular type)
Autosomal DOMINANT
Col3a1
arterial, intestinal, uterine rupture

Question 4

Systemic JIA

Answer 4

Still’s disease
- rash, high fever, multiple inflamed joints
- anemia, high wbc
- serositis, heptosplenomegaly, lymphadenopathy, pericarditis
- ages 5-10, girls=boys
- least common type of JIA, with poorest prognosis

Question 5

Pauciarticular JIA

Answer 5

most common
four or less joints involved
limp that gets better thruout day
can have LLD
large joints more common - knees/ankles
peak age 2-3
Girls 4x boys
20% have UVEITIS
- ophtho eval ever 4 months if ANA positive, 6 months if ANA Negative

Question 6

Polyarticular JIA

Answer 6

5+ joints involved
small joints commonly affected
less frequent uveitis
girls>boys

Question 7

ankylosing spondylitis

Answer 7

age of onset 15-35
HLA B-27
Sacroilitis, enthesopathies, bamboo spine, uveitis

Question 8

Psoriatic arthritis

Answer 8

PENCIL IN A CUP phalangeal deformity
nail pitting
dactylitis

Question 9

reactive arthritis

Answer 9

IMMUNE COMPLEX mediated
reaction to chlamydia, yersinia, salmonella, campylobacter, shigella
- associated with conjunctivitis and dysuria

Question 10

Hypophosphatemic rickets

Answer 10

Most common type in the United States

X-­linked dominant, impaired renal phosphate ABSORPTION

Decreased phosphate
NORMAL calcium, PTH and vitamin D
increased alkaline phosphatase

Tx: High-­dose phosphate and vitamin D
Burosumab FGF-­23 antibody

Question 11

Vitamin D deficient rickets

Answer 11

NUTRITIONAL Deficiency

Decreased vitamin D, calcium, and phosphate;
increased PTH and alkaline phosphatase

Vitamin D replacement

Question 12

Vitamin D 
dependent, type 1

Answer 12

Autosomal recessive

Defect in RENAL 25-­hydroxyvitamin D 1-­α-­hydroxylase

Low calcium and phosphate
NORMAL 25-­hydroxyvitamin D
very low 1,25-­dihydroxyvitamin D
high alkaline phosphatase and PTH

Tx: 1,25-­Dihydroxyvitamin D replacement

Question 13

Hypophosphatasia

Answer 13

Autosomal recessive

deficient or nonfunctional alkaline phosphatase

Increased calcium and phosphate levels
very low alkaline phosphatase levels
normal PTH/vitamin D levels

early tooth loss

tx: Asfotase alfa

Question 14

Genetic defect in trisomy 21

Answer 14

maternal duplication of chromosome 21

Question 15

phenotype trisomy 21

Answer 15

flattened face
upward slanting eyes
epicanthal folds
SINGLE palmar crease

Congenital heart disease:
- endocardial cushion defects in 50%

duodenal atresia
hypothyroidism
hearing loss
ligamentous laxity
high incidence of leukemia/lymphoma

Question 16

spine features of trisomy 21

Answer 16

ATLANTOAXIAL INSTABILITY
- if ADI >5 and symptomatic, or >10 and asymptomatic
scoli most common, least dangerous
spondylolisthesis

Question 17

lower extremity manifestations of trisomy 21

Answer 17

metatrsus primus varus
pes planovalgus
hallux valgus
patellar dislocation/instability
late onset hip instability

Question 18

osteogenesis imperfecta

Answer 18

Col1a1 and 1a2 genes
decreased number of trabeculae and decreased cortical thickness

Types: ALL are autosomal dominant (90% of patients are type I or IV)
I: least severe - quantitative disorder
II most severe - qualitative disorder
III: most severe survivable form - qualitative
IV: moderate severity normal hearing - qualitative

Question 19

Spine manifestations of OI

Answer 19

*** type II and III (most severe forms II always lethal in childhood)
BASILAR INVAGINATION
severe scoli

Question 20

Gaucher’s disease

Answer 20

B-glucocerebrosidase deficiency -> macrophages stuffed with glucocerebrosides
- MSK manifestations
erlenmeyer flask distal femurs
osteonecrosis of the hips/femoral condyles
cortical thinning

Question 21

Caffey’s diesease

Answer 21

FEBRILE illness, hyperirritable

hyperostosis of infancy
average age of onset - 9weeks
self resolving, diagnosis of exclusion
kids often get NAT workup
esr and alkphos are elevated

MANDIBLE involvement is pathognomonic
forearm (ulna) next most common
VERTEBRA AND PHALANGES ARE NOT INVOLVED