A carbuncle found on the back of the neck of a patient. It is formed by a cluster of interconnected boils, which are painful, pus- filled, inflamed hair roots. Carbuncles are usually caused by the bacterium Staphylococcus aureus and other common sites are the buttocks. Carbuncles are less common than single boils. They mainly affect people with a lowered resistance to infections in particular, as in this case, people with diabetes mellitus. They are treated with antibiotic drugs and occasionally it is necessary to incise the carbuncle and drain the pus.