Dermatomyositis

Dermatomyositis (DM) clasically presents with a periorbital heliotrope rash, but at times the purple discoloration is not seen and the diagnosis of DM is one to consider in a patient with periorbital oedema. The finding of erythematous papules over the knuckes (Gottren's papules), linear erythema along the dorsal surface of the fingers, and ragged, erythematous nailfolds indicates DM.

There is often a detectable proximal myopathy and patients will struggle with activities that involve lifting their arms above the shoulders, as in this case. There is an association with malignancy, particularly lung and upper aerodigective tract. The patient's cough suggests he may have an underlying lung cancer.

Differential

Hypothyroidism can cause periorbital oedema and a proximal myopathy but doesn't explain the rash.

PAN often presents with middle aged men and could explain his cough but causes myalgia and a vasculitic rash.