Fact-sheet: Dermatomyositis
  • Dermatopolymyositis


Updated on 04/26/2023 at 7:09 PM

Note : 0/10
Share

View all RADEOS cases associated with this fact-sheet

Definition

3 types of lesions
-Inflammatory lesion
-Atrophy
-Fatty degeneration
Distribution:
Polymyositis: symmetric involvement, proximal predominance, predominance in the posterior muscle group or diffuse involvement.
Inclusion body myositis: preferential involvement of the quadriceps, asymmetric involvement.

Clinical features

Female predominance (2:1)

Two age peaks: 5-14 years and 5th-6th decades

Motor deficit comparable to that seen in polymyositis (myogenic, bilateral and symmetric, predominating in proximal muscles), associated with dermatologic lesions: periorbital erythema and edema and/or involvement of sun-exposed areas, Gottron papules

Associations with:

  • Subcutaneous calcinosis producing a subcutaneous armor-like plate, almost exclusively in children
  • Intramuscular fluid collections

Radiography

Possible acro-osteolysis of the terminal phalangeal tufts

Calcium deposits

MRI

Confirms the presence of muscle involvement. The sensitivity of MRI for the diagnosis of myositis ranges from 70 to 100%.

Centered on symptomatic regions (particularly the limb girdles) or whole-body.

T1: assess for muscle atrophy and/or fatty degeneration.
STIR: muscle edema = indirect and nonspecific marker of muscle inflammation.

T2-Dixon +++: simultaneous detection of atrophy (on Fat images) and edema (on Water images).

Imaging features similar to those of polymyositis:

  • more pronounced proximal involvement, global but non-uniform, symmetric
  • involves the posterior muscle groups or all muscles
  • tendency for muscle abnormalities to predominate adjacent to the fascia
  • inflammation generally more pronounced than atrophy and fatty degeneration
  • possible associated fasciitis
  • + skin involvement (not present in polymyositis), inflammatory or calcifications

Management

Biopsy not systematic if presentation is atypical.

Surgical biopsies requiring sampling of a large amount of muscle tissue.

Differential diagnosis

Inclusion body myositis: preferential involvement of the anterior muscle groups