Diabetes mellitus:

Diabetes mellitus can have a number of cutaneous features. Complications of diabetes itself include:
fungal infection (e.g. candidiasis)
bacterial infections (e.g. recurrent boils)
xanthomas
arterial disease (ulcers, gangrene)
neuropathic ulcers.
Specific dermatoses of diabetes include:
necrobiosis lipoidica (a patch of spreading erythema over the shin which becomes yellowish and atrophic in the centre and may ulcerate)
diffuse granuloma annulare (p. 1336)
diabetic dermopathy (red-brown flat-topped papules)
blisters (usually on the feet or hands)
diabetic stiff skin (tight waxy skin over the fingers with limitation of joint movement owing to thickened collagen - also called cheiroarthropathy).