Dermatomyositis

Question 1

epidemiology

Answer 1

female predominance, bimodal peaks (childhood age 5-14 yo and adulthood age 45-65 yo)

Question 2

what polymorphism is a/w juvenile dermatomyositis ?

Answer 2

TNF alpha 308A

Question 3

what drugs can induce dermatomyositis? **

Answer 3

hydroxyurea + statins (+cyclophosphamide, d-penicillamine, BCG vaccine, and TNF alpha inhibitor).

FYI the former has delayed latency (starts 60 months after using drug), while the latter drugs have an onset of 2 months. The latter + myositis, while the former - myositis. Both forms resolve within 1-2 months of medication cessation

Question 4

features of muscle disease **

Answer 4

(1) symmetric proximal muscle weakness (extensor> flexor), but NO myalgia
(2) often affects shoulders, hip girdle, and neck flexors
(3) may have difficulty walking up stairs or brushing hair

Question 5

features of skin disease **

Answer 5

(1) gottron’s papules (lichenoid papules over knuckles)
(2) facial erythema and malar edema
(3) heliotrope sign on eyelids w/ periorbital edema
(4) Shawl or “V” sign
AND MOST IMPORTANTLY SEVERE PRURITUS!!

Question 6

features of nail changes**

Answer 6

ragged cuticles, periungual erythema, and prox nail fold w/ symmetric dilated capillary loops alternating with areas of vessel dropout

*unlike SLE with glomeruloid capillary loops

Question 7

DM classification for adults **

Answer 7

(1) classic (2) cancer- associated (3) DM overlap syndrome (4) Amyopathic DM (5) hypomyopathic DM

Question 8

DM classification for kids (aka juveniles)

Answer 8

(1) classic juvenile DM (2) Amyopathic DM (3) hypomyopathic DM

Question 9

What are the features of classic DM for adults? **

Answer 9

classic skin findings +/- muscle disease. a/w interstitial lung dz + anti-CADM-140 (MDA5)

Question 10

What are the features of cancer-associated DM for adults? **

Answer 10

a/w anti-p155/140 autoAb AND
anti-T1F-1 AND anti-SAE

ovarian and GI cancer (specifically colon ca)***; nasopharyngeal cancer in those of asian descent. Cancer risk mostly returns to normal within 5 years after diagnosis (except for GI cancers)

Question 11

What are the features of DM overlap syndrome adults?

Answer 11

DM + lupus/sjogren/scleroderma => anti-Ku
DM or polymyositis + scleroderma =>anti-PM/Scl (PM-1)
DM + other CTD => anti-U1-RNP

Question 12

What are the features of anti-synthetase syndrome, a subtype of DM? *******

Answer 12

a/w interstitial lung dz + mechanics hands clinically page 110/111

Question 13

common sequelae in adult DM vs. juvenile DM?

Answer 13

adult DM –> cancer; juvenile DM -> calcinosis cutis (brunsting variant, responds well to oral steroids) and vasculitis (banker variant, poor prognosis)

Question 14

lab tests

Answer 14

elevated ANA (in 40% of cases), high CK, high aldolase, myositis specific Ab

CK- most sensitive muscle enzyme

Question 15

treatment

Answer 15

• for muscle - always ORAL STEROIDS.
• for skin only - photoprotection, topical steroids, calcineurin inhibitors, +/- antimalarials.
• caution with antimalarials as these have decreased efficacy and increased risk of drug eruption in DM patients

Question 16

dermpath findings

Answer 16

vacuolar interface, epidermal atrophy, thickened BMZ, dermal mucin deposition, and sparse PV/PA lymph infiltrate

Question 17

DM myositis specific Ab

Answer 17

(1) anti-CADM-140 (MDA5) - seen in classic adult and juvenile DM, both are a/w progressive lung disease
(2) anti-p155/140, anti-T1F1: seen in cancer assoc DM in adults + classic juvenile DM w/ extensive skin disease
(3) anti-p140/-NXP2 seen in juvenile DM with calcinosis cutis + contractures
(4) anti-synthetase - seen in adult DM subtype; patients have severe lung dz + mechanic’s hands
(5) Anti-Mi2; DM with best prognosis and less severe disease
(6) anti-SRP: linked to acute onset necrotizing myopathy with severe weakness and high CK
(7) anti-Ku: DM overlap with SLE, SSc, and Sjogren’s
(8) anti-U1RNP: mixed connective tissue disorder
(9) anti-PM/Scl (PM-1): DM/PM + scleroderma
(10) anti-SAE: seen in clinically amyopathic DM

Question 18

anti-synthetase (mechanic’s hands) include the following:

Answer 18

anti-Jo1, anti-PL7, anti-PL12, and EJ/OJ

Question 19

Gottron’s vs. acute CLE hand findings

Answer 19

in DM, there are gottron’s papules which overly the knuckles. in ACLE, the lesions spare the knuckles