In some cases dark patches or discolouration of the skin in the neck could be a sign of diabetes or a fungal infection which needs to be treated. And hence it is important to know what the dark patches on the neck indicate. Dr Pradip Shah consultant physician Fortis Hospital Mulund Mumbai lists three common skin conditions that dark patches on the neck indicate and when to take them seriously. Acanthosis nigricans: It is a common skin condition seen in people who have type 2 diabetes. Also know as dirty neck syndrome there is brown to black hyperpigmentation of the