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Dermatomiosite

Classification: idiopathic inflammatory myopathies
  • Importance: potentially serious muscle damage, pulmonary manifestations, strong association with neoplasm in adults 💀
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Etiologia: desconhecida
  • Immune mediated process
  • Triggered by “outside” factors
    • Malignancy
      • Associated with NXP2 and TIF1-gama
      • Associated specially in amyopathic forms
      • No risk in juvenile form
      • Genitourinary (ovarian)
      • Colon
      • Nasopharyngeal (in asians)
      • Lung, gastric, pancreatic, lymphomas
    • Drugs
    • Infectious agents
 
Epidemiologia
  • Incidence: 1 per 10.000 person-years (increasing?)
  • Bimodal age distribution
    • Juvenile form: 5-15 anos
      • Absence of associated cancer
      • Higher frequency of visceral complications (gastrointestinal ulcer, glomerulonephritis, purpura, polyadenopathy)
    • Adult form: 50-60 anos
  • F:M = 2:1
 
Classification
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Apresentação clínica
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  • Cutaneous
    • Distinctive, photodistributed, pink-violet (Violaceous, lilac) poikiloderma rash
      • Face rash - diffuse erythema
        • May or may not spare nasolabial fold
        • DDx: allergic contact dermatitis, rosacea, seborrhoeic dermatitis, lupus erythematosus
      • Heliotrope erythema - eyelids
        • Edema may be present
        • Periocular edema - key to diagnosis - heliotrope ras
        • Area on the medial canthus in lower eyelid - classical of MDA-5 phenotype (study in King’s Hospital) - look for lung disease
      • V-sign (chest)
        • Can involve the V of the neck
    • Gottron sign (elbows or knees)
    • Gottron papules
      • Papules on the knuckles with secondary lichenoid quality
      • DDx: no lupus é o inverso, as lesões estão entre as articulações e poupam as falanges
    • Shawl sign (upper back)
    • Holster sign (lateral thigh)
    • Mechanic’s hands (association with anti-synthetase syndrome)
      • Periungueal telangiectasias
        • Dilated capillary loops alternate with capillary dropout
      • Centripetal flagellate erythema
      • Pruritus (may help distinguish from LE)
      • Unspecific
        • Calcinosis cutis (++ juvenile form)
          • Psoriasiform eruption in scalp
          • Diffuse non-scarring alopecial with scaling (++occipital)
      • Extracutaneous
        • Musculares 💪
          • Proximal symmetrical myopathy
            • May be slightly painful (inflammatory)
            • Onset usually after cutaneous symptoms
          • Cardiac involvement
            • Arrythmias
          • Esophageal involvement
            • Dysphagia, GERD
            • should prompt evaluation for overlap with systemic sclerosis
        • Polyarthritis
        • Pulmonary disease 🫁
          • Do PFTs with DLCO in all patients
          • If MDA5 positive also do high resolution CT chest
          • Also in anti-synthetase syndrome (anti-Jo1)
          • Coarse of pulmonary involvement is usually independent from corticosteroids and can affect prognosis
        • Malignancy-related
          • x10-40 risk
          • Most malignancies diagnosed in the first year, after 5 years rare
          • Factors positively associated with cancer
            • Antibodies: NXP2 and TIF1-gama
            • amyopathic forms
          • Factors negatively associated with cancer
            • juvenile onset
            • lymphopenia
            • anti-Mi2 antibodies
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      Exames complementares de diagnóstico
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      • Anticorpos
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        • ANA positive in ~70%
        • Myositis-Associated Abs (MAA) - not specific, support diagnosis, can also be found in other autoimmune diseases
          • Ro
          • La
          • U1-RNP
          • U3-RNP
          • PM-Scl
        • Myositis-specific Abs (MSA) - specific, define phenotype
          • Mi-2
            • Most specific antibody
            • Linked to cutaneous findings (shawl sign, cuticular changes) and milder muscle disease with more faborable prognosis
          • TIF-1 gama
          • MDA-5
          • SAE
          • NXP-2
          • Jo-1
            • É um anticorpo antisintetase
              • Anticorpos anti-sintetase (Jo-1, PL-7, PL-12) são dirigidos a antigénios citoplasmáticos e conferem risco de doença pulmonar intersticial
        • Histologia
          • Pode ser semelhante ao lupus
            • Espessamento membrana basal
            • Pode ter padrão de interface vacuolar
              • Deposição de mucina
            • Músculo: lymphocytic myositis
          • Se suspeita de malignidade
            • Nos dias de hoje mais modernos: TC-CTAP ou PET-CT
            • O classico era:
              • CXR
              • Colonoscopy in Bolognia (in Saurat: stool blood test → upper and lower endoscopy if positive)
              • Mamography, gynecological U/S, serum CA125
              • ENT examination
              • Rectal examination + PSA
            • Vigiar malignidade anualmente até 5 anos após o diagnóstico
          • Músculo
            • CK, LDH, AST/ALT, aldolase
            • EMG
            • MRI (bilateral thigh) or U/S
            • Muscle biopsy
              • Deltoid usually done by surgeon for convenience
              • Triceps is better
          • Intersticial lung disease
            • CXR
            • Functional pulmonary tests with DLCO
            • high resolution CT if MDA5
          • Cardiac
            • U/S, EKG
          • Esophageal
            • Barium swallow or manometry
          Diagnóstico
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          DDx
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          Avaliar severidade
          • DSSI: Dermatomyositis Skin Severity Index
          • CDASI: Cuteanous Dermatomyositis Disease Area and Severity Index
          Tratamento
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          • Discordance between muscle disease and skin disease response to systemic therapy
            • Not all patients remit cutaneous lesions when muscle disease remits
          • Adults should have apointments every 4-6 months for 3-5 years with complete physical to screen for malignancy
          • Skin
            • Emoliente + soap substitute
            • Photoprotection
            • Steroid ointment (not very helpful)
            • Eyelids
              • Protopic
              • Elidel
            • Itch
              • High dose antihistamine (fexofenadine 180mg)
            • Facial redness & flushing
              • Clonidine (50mcg TDS) - studied for rosacea, but not helpful
            • Systemic medications
              • Hidroxicloroquina
              • MTX
              • IVIG, Micophenolate mophetil
            • Calcinose cutis (++ dermatomiosite juvenil)
          • Myositis
            • = treatment for skin
            • Prednisolone + immunosuppressant
              • Prednisone 1mg/kg/dia (belief that a slow taper over 6-8 to 24-48 months can make patient muscle disease free)
                • Prevent osteoporosis
              • MTX
              • Micofenolato
              • Tacrolimus
            • Rituximab
              • Fantastic for myositis, not for skin
            • Abatacept: failed 1st end-point
              • Can be helpful for calcinotic disease
            • IVIg
              • Safe, quick
              • Very costly
            • Cyclophosphamide
            • JAKi
              • Bom nos overlap com dermatite atópica
           
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