Dermatomyositis
This is a chronic inflammation of skin and muscles.
Presentation
Presents with the features of Polymyositis (bilateral, proximal muscle weakness, pain, and fatigue) + Skin features:
Heliotrope rash (lilac discolouration of eyelid with peri-orbital oedema)
Gottron lesions (scaly erythematous patches) on joints
Macular erythematous rash
Investigations
Key finding here is a Raised CK. This can, however, also be caused by rhabdomyolysis, AKI, MI, statins, and strenuous exercise.
Other investigations:
EMG – Confirms myopathic cause, and excludes a neuropathic cause
Anti-Jo-1, Anti-Mi-2
A Muscle biopsy is needed for a definitive diagnosis, and will show inflammatory infiltrates in the muscle.
Management
Corticosteroids.
Immunosuppressants/DMARDs e.g. methotrexate can be used as an adjunct here to make it easier for the steroids to work, therefore not needing as high a dose
Important Links:
https://dermnetnz.org/topics/adult-onset-dermatomyositishttps://bestpractice.bmj.com/crawler/topics/en-gb/595 “Gottron's papules. Erythematous to violaceous raised papules overlying the metacarpal and interphalangeal joints in a patient with juvenile dermatomyositis.” © Elizabeth M. Dugan, Adam M. Huber, Frederick W. Miller, Lisa G. Rider CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)
“A hallmark (i.e., pathognomonic) sign of dermatomyositis, consisting of violaceous to erythematous discrete or confluent macules confined to the upper eyelids. An eruption with similar characteristics can extend periorbitally. Heliotrope is often associated with periorbital edema and telangiectasias of the upper eyelids. In the resolution stage, atrophy or dyspigmentation (hypo- or hyperpigmentation) may be apparent. Heliotrope. Subtle erythema and minimal edema involving both upper eyelids, with extension to the lower eyelids.” © Elizabeth M. Dugan, Adam M. Huber, Frederick W. Miller, Lisa G. Rider CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)