Dermatomyositis

Which is the most common presenting symptom in dermatomyositis?

Muscle weakness is the most common presenting symptom in dermatomyositis.

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Which is the initiating event in pathophysiology of Dermatomyositis?

Initiating event in pathophysiology of Dermatomyositis is the activation of completer factor-3 (C3), which forms C3b and C4b.

Followed by the formation of the neoantigen C3bNEO and the C5b-C9 membrane attack complex (MAC).

Results in humoral mediated attack directed against the muscle capillaries and the endothelium of arterioles. 

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What are the Pathognomonic findings of dermatomyositis?

Gottron papules: dorsal metacarpophalangeal and interphalangeal joints may show the presence of overlying erythematous or violaceous papules with or without scaling or ulceration.

Heliotrope rash: This is a characteristic skin finding of dermatomyositis and presents with a violaceous, or an erythematous rash affecting the upper eyelids with or without periorbital edema. This finding may not be apparent in patients with dark skin patients.

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What are the Skin findings that may help differentiate dermatomyositis from other conditions?

Gottron sign: erythematous macules or patches over the elbows or knees
Facial erythema: erythema over the cheeks and nasal bridge involving the nasolabial folds. The rash may extend up to the forehead and laterally up to the ears.

Shawl sign: erythema over the posterior aspect of the neck, upper back, and shoulders at times, extending to the upper arms.

V sign: ill-defined erythematous macules involving the anterior aspect of the neck and the upper chest.

Poikiloderma: atrophic skin with changes in pigmentation and telangiectasia in photo-exposed or non-exposed areas.

Holster sign: poikiloderma involving the lateral aspects of the thighs.

Periungual involvement: telangiectasias and cuticular overgrowth

Mechanic’s hands: hyperkeratotic, cracked horizontal lines on the palmar and lateral aspects of the fingers.

Scalp involvement: diffuse poikiloderma, with scaling and pruritis.

Calcinosis cutis: calcium deposits in the skin