Acanthosis nigricans - your black neck can be a sign of Diabetes.

The skin manifestation of acanthosis nigricans is darkening of the neck along with some degree of skin thickening. Other than neck it is often seen in the armpit and groin as well. Children can also be affected. AN (Acanthosis nigricans) should be suspected whenever you find black thickening of the neck or armpit in an overweight person. 

Of Course all black necks are not due to AN. Many other diseases including common ones like Atopic dermatitis (a type of allergy in children) or some type of fungal infection can produce similar pictures. However physicians can usually tell whether it is AN just by looking at it. So when in doubt, it is the best idea to visit a doctor.

To understand the relationship of AN with diabetes, you need to know a very basic knowledge of how AN develops.

The thickening and blackening of skin is actually due to some abnormal growth of certain types of cells in your skin in response to some chemicals that come via your blood and then stimulates the growth of those cells. Insulin (the hormone which becomes deficient in diabetes) is one of such chemicals.

Now, when someone gains weight, an interesting thing happens. You probably know that insulin is an essential hormone that needs to act on every cell of your body to insert glucose inside the cell (the glucose will help in energy production , which will keep the cell alive). But they are less effective on fat cells. So when the number of fat cells in your body increases, insulin would find it difficult to do its work effectively. In response, your body would then increase insulin production to handle the job. It will thus produce the abnormal skin darkening and thickening as explained in the last paragraph.

So, when does Diabetes come into the picture ? Actually if the process continues, and the body keeps producing high levels of insulin for a long time, eventually it will end up destroying its own insulin producing cells and then diabetes (Type II) will develop. 

So technically AN (acanthosis nigricans) can be regarded as an indirect sign that diabetes might develop soon (or has already developed). How can we be certain of that ? If diabetes has already developed, then there will be an increased level of glucose in your blood (as not enough insulin is there to push them inside the cells), or if it is yet to develop then there will be an increased level of insulin in your blood (as explained before). If the latter is the case, it indicates pre-diabetes and there is still a chance that you can prevent diabetes from happening if you can reverse the process. So physicians often perform those tests (Fasting blood glucose level and Fasting insulin level - fasting because food will hamper the level ) to be certain.

In this era of junk-foods, health-drinks and social media , it is very common that teenagers are gaining abnormal weight. They are mostly at the stage of pre-diabetes (increased blood level of insulin) and it is possible through a healthy lifestyle and weight reduction, that they can reverse the stage and prevent a deadly disease like diabetes from happening.

Theoretically, there are many conditions (as described in medical textbooks) that might be the cause of AN apart from obesity but they are usually very rare (means that you should let your doctor worry about it (if needed) and stop doing research yourself ! )

If you still want to intuitively understand what might be the other causes, recall the mechanism behind AN from the last section, it happens when certain cells of your skin get over-stimulated due to certain chemicals like insulin. 

1. Insulin is not the only chemical. There are other chemicals that just act like it and stimulate those cells. 
2. Due to certain genetic defects in those cells, they might get over-stimulated even to the normal amount of those chemicals.
3. There are many other reasons (apart from obesity) that might cause a high insulin level in your blood.

So it is important that when you visit a doctor you answer all his/her questions correctly including any other disorder / symptoms you have or any other medicine you are taking.

It is always a good idea to maintain a healthy weight through diet and exercise (even when you do not have acanthosis nigricans). (Check if you have healthy weight)

So if you are overweight, the best course of action is to lose some weight gradually.

You can lose weight when the calorie you lose will be more than the calorie you gain.

To lower the calorie gain, you need to limit your food intake. Specially those with high calorie such as carbohydrates like rice or bread as well as junk foods. 

Actually the food type has a deeper association with AN or diabetes which is beyond the scope of this article. For the sake of simplicity, just remember the rule of thumbs : the more some food is processed (Away from its natural state, though it usually makes it more tasty) , the more harmful it is. For example brown rice is less harmful than fine white rice. That’s why pizza and burgers are harmful as they are made of refined and processed flour. Sugar is processed from sugar cane plants so food that contains high amounts of free sugar (such as cold-drinks) are much more harmful than fruit juices or coconut water (as they are naturally derived).

You can take help from our diet chart maker to make an appropriate diet chart for you or if that seems too complex, taking help from a dietitian would be better.

The other way to tilt the calorie equation is ofcourse to increase the calorie you lose. The way people lose their calorie is usually by two ways.

1. Body needs to spend some calories (energy) for its own needs (to maintain the work it does , like to pump the heart). We call it Basal Metabolic Rate or BMR. This is something you can not control usually. However in certain diseases this can be abnormally low (like hypothyroidism - lower amount of thyroid hormones in your blood) for which you should get treatment to keep the BMR level normal.
2. The other way is of course through physical activity. The trick is to live a physically active life overall rather than doing some routine exercise as your goal is not to develop muscles here. Every physical activity you do is an opportunity to lose some weight (look at this chart).

Along with the advice of weight loss, your doctor might give you some specific treatments for the conditions. However, please remember that weight reduction is still the best mode of treatment.

Here are some possible medicines your doctor might advise.

1. Topical creams : topical creams are usually given to either stop the stimulation of your thickened skin cells or exfoliate them rapidly. Some of the creams used are tretinoin , adapalene , calcipotriol and ammonium lactate or urea based moisturizers.
2. Oral medicines are sometimes given for two reasons. One group of medicine ( example : acitretin) acts on the cells to lower their stimulation level and also helps in their rapid exfoliation. Other groups of medicines usually decrease the effect of insulin on the cell directly. The second group, as you might probably guess, are usually the drugs for diabetes (example : metformin) but can be given even if your blood glucose level is normal but insulin level is high. Certain other chemicals are also used such as alpha-lipoic-acid. 
3. Some cosmetic procedures like Lasers (alexandrite , erbium , co2) and chemical peels (glycolic acid , Trichloroacetic acid) are also used for AN. They basically act by just destroying and removing the affected cells. So though they can quickly improve the appearance, cosmetic procedures alone can not sustain the result as the underlying disease process keeps going on.