Autoimmune Myopathies

Question 1

What is juvenile dermatomyositis?

Answer 1

A systemic connective tissue disorder with chronic skeletal muscle and skin inflammation.

Question 2

What is polymyositis?

Answer 2

An inflammatory myositis that does not have associated skin involvement.

Question 3

What is the typical age distribution for the incidence of autoimmune myopathies?

Answer 3

There is a bimodal pattern of incidence, peaking first at 3-7 years and again in the early teenage years.

Question 4

How do patients with juvenile dermatosytis usually present?

Answer 4

Patients present with a rash and muscle weakness which gradually develop over weeks to months.

Question 5

Describe the classic rashes of juvenile dermatomyositis.

Answer 5

The typical rashes include the classic heliotrope (faint purple-to-red discoloration of the eyelids, with or without periorbital edema) and Gottron papules (red plaques over the extensor surfaces - most commonly occurring over the small joints of the hands). ***Include Image 20-12 and 20-13

Question 6

What periungual changes can be seen in juvenile dermatomyositis?

Answer 6

Cuticular overgrowth and dilated tortuous capillaries by capillaroscopy.

Question 7

The muscle weakness of juvenile dermatomyositis mainly affects which muscle groups: proximal or distal?

Answer 7

The muscle weakness is always proximal and symmetric in nature.

Question 8

What joint finding occurs in ~70% of patients with juvenile dermatomyositis?

Answer 8

Arthralgias. Arthritis can occur as well but is less common.

Question 9

List three examples of the type of weakness you would expect to see in patients with juvenile dermatomyositis.

Answer 9

You would expect proximal, symmetric weakness: difficulty in grooming hair, getting up off the floor, and climbing stairs.

Question 10

List three potential complications of juvenile dermatomyositis.

Answer 10

Ulcerative skin lesions, GI vasculitis, and dystrophic calcification of the skin (calcinosis cutis).

Question 11

Which complication of juvenile dermatositis is most serious and life-threatening?

Answer 11

GI vasculitis

Question 12

What are the (2) risk factors for developing complications from juvenile dermatomyositis?

Answer 12

Inadequate steroid therapy and delay of therapy for > 4 months from onset of myositis.

Question 13

What physical exam finding is a poor prognostic sign in patients with juvenile dermatomyositis?

Answer 13

Ulcerative skin disease is a poor prognostic sign and can portend GI vasculitis (which is one of the most life-threatening complications of JDM).

Question 14

What is the primary therapy for juvenile dermatomyositis?

Answer 14

Prednisone 2-3 mg/kg/day.

Question 15

What alternate therapy is used by some rheumatologists to treat severe cases of myositis in patients with juvenile dermatomyositis?

Answer 15

Methylprednisolone 30 mg/kg/dose IV for ≥3 doses.

Question 16

What three adjunctive therapies can be used in the management of skin rash from juvenile dermatomyositis?

Answer 16

Sunscreen, sun avoidance, and hydroxychloroquine.

Question 17

What are the diagnostic criteria for Juvenile Dermatomyositis?

Answer 17

Presence of heliotrope rash or Gottron papules is required + at least 3 of the following 4 findings for definite diagnosis OR at least 2 of the following 4 findings for probable diagnosis: Symmetric proximal muscle weakness; elevated CPK, aldolase, LDH, or transaminases; EMG abnormalities; and muscle biopsy abnormalities.

Question 18

What diagnostic modality may be used in place of EMG in helping to make a diagnosis of juvenile dermatomyositis?

Answer 18

MRI of the thigh muscles, demonstrating inflammation as symmetric muscle edema.

Question 19

List 5 possible findings on muscle biopsy in patients diagnosed with juvenile dermatomyositis.

Answer 19

Degeneration, regeneration, necrosis, phagocytosis, and interstitial mononuclear cell infiltrate.

Question 20

List three potential EMG patterns which would be consistent with a diagnosis of juvenile dermatomyositis.

Answer 20

Small amplitude, short duration, polyphasic motor-unit potentials; fibrillations, positive sharp waves, increased insertional irritability; spontaneous, bizarre, high-frequency discharges.

Question 21

What is the typical disease course in patients with juvenile dermatomyositis after treatment initiation?

Answer 21

About 60-80% of patients recover after their first episode or after ≥1 recurrences. Fewer than 20% have difficult to control disease with persistent myositis over a long period of time.

Question 22

What is the relationship between juvenile dermatomyositis and development of malignancy?

Answer 22

Unlike adult dermatomyositis, in which the dermatomyositis is often a paraneoplastic syndrome, juvenile dermatomyositis rarely predisposes to malignancy, and routine screening for malignancy is not required.

Question 23

Compare the incidence, presentation, and outcome of juvenile polymyositis with that of juvenile dermatomyositis.

Answer 23

Juvenile polymyositis is extremely rare. It presents like juvenile dermatomyositis but without skin findings. It typically has a chronic course, in contrast to JDM, which usually resolves after the initial episode is treated.