Why can't I wash off the "mud" on my neck? Doctor: This is not mud, be careful of these diseases

My friend was a little worried recently because he accidentally found that his little fat boy's neck and armpits were black, as if there was accumulated dirt. He thought that the boy didn't take a good bath, but after careful supervision, he found that the "dirt" could not be washed off, which made him realize that something was wrong.

Out of caution, I asked my friend to take Xiaopang to a dermatologist. But based on the dirt-like appearance, the location of the disease, and Xiaopang's body shape, I had already guessed that Xiaopang was most likely suffering from acanthosis nigricans, and the feedback from the dermatologist later confirmed my judgment.

Acanthosis nigricans is not uncommon. You may have seen children who look “dirty”. Most of them are fat children. Obesity is one of the important causes of acanthosis nigricans, and it is especially evident in children and adolescents. [1]

A survey of 618 people aged 7 to 17 years showed that the incidence of acanthosis nigricans was positively correlated with obesity. Among children in the top 2% of body mass index, 62% had acanthosis nigricans. [2]

01

What is acanthosis nigricans?

Acanthosis nigricans is a disease that causes the skin to become dark brown and rough. The lesions are usually symmetrically distributed in the intertriginous areas of the body, which are places that are easily rubbed. The back of the neck, the sides, and the armpits are the most common. Other areas with skin folds such as the elbows, under the breasts, in the groin, and around the navel can occasionally be seen.

The lesions often thicken and take on a velvety appearance, and sometimes there are scattered wart-like skin tags. Most cases of acanthosis nigricans are asymptomatic, but if the affected area is soaked in sweat, the skin may become infected, inflamed, itchy, painful, and oozing.

02

Why does acanthosis nigricans occur?

Although acanthosis nigricans looks dirty, it has nothing to do with personal hygiene and you should not be prejudiced against patients because of its appearance.

There are many factors that induce acanthosis nigricans. As mentioned above, the occurrence of acanthosis nigricans is related to obesity, and the characteristics of the distribution of the sites show that it may also be related to local physical stimulation of the skin. Acanthosis nigricans can occur in both children and adults. In addition to obesity, genetics, race, and type 2 diabetes are also risk factors for acanthosis nigricans, among which hyperinsulinemia and insulin resistance seem to play a crucial role. [2-4] Some malignant tumors and drugs can occasionally cause acanthosis nigricans. [5-8]

03

What situations are likely to cause acanthosis nigricans?

What might the presence of acanthosis nigricans indicate?

We all know that the function of insulin is to lower the level of glucose in the blood. But sometimes, the ability of insulin to lower blood sugar decreases due to various reasons, so the body has to secrete more insulin to maintain stable blood sugar. This is the process of insulin resistance and hyperinsulinemia.

Diabetics, "quasi-diabetics" with impaired glucose tolerance, and obese people may all suffer from insulin resistance and hyperinsulinemia, making them the most common group of people suffering from acanthosis nigricans.

Although PCOS patients mainly present with menstrual abnormalities and hyperandrogenism, a considerable number of them also suffer from obesity and insulin resistance, as PCOS is essentially a syndrome of a series of metabolic problems. Clinically, it has been observed that up to one-third of PCOS patients have acanthosis nigricans. [9]

Similarly, drugs that affect blood sugar metabolism and insulin levels, such as injectable insulin and systemic glucocorticoids, can naturally cause acanthosis nigricans.

So on the other hand, if you suddenly notice that the skin color on the back of your neck and underarms darkens symmetrically, and you suspect it is acanthosis nigricans, what should you do?

1. Review the medications you have taken recently to see if any of them affect sugar metabolism or have adverse reactions including acanthosis nigricans.

2. Check blood sugar, insulin, glucose tolerance and other blood sugar metabolism related indicators.

3. If combined with menstrual abnormalities, sex hormone levels and gynecological B-ultrasound should also be checked.

It’s easy to think of, right? This is how it is done clinically. For example, some doctors recommend using acanthosis nigricans as a predictor of gestational diabetes. [10]

However, the culprit of acanthosis nigricans is not always abnormal insulin and blood sugar. At present, some cases of hereditary acanthosis nigricans have been found to be related to specific gene mutations, and some malignant tumors can also cause acanthosis nigricans or similar symptoms. Therefore, if you have not taken medication recently, and your weight, blood sugar and other related indicators are normal, but you still develop acanthosis nigricans, you need to be extra careful.

04

Treatment of acanthosis nigricans

Finding and solving the original problem is the key to treating acanthosis nigricans. Obese patients should control their weight, patients with abnormal blood sugar should pay attention to improving insulin resistance, and replace or stop using the drugs that cause acanthosis nigricans. The situation will naturally improve. If the current situation cannot be changed for the time being, there are also drugs that promote skin metabolism, laser and other treatments that can help improve the skin condition.

As a disease, acanthosis nigricans is more like an external indicator of abnormal physical condition. So if you or your family members are infected, you must carefully investigate the reasons behind it and eliminate health risks.

References:

[1] Sinha S, Schwartz RA. Juvenile acanthosis nigricans. J Am Acad Dermatol. 2007;57(3):502-508. doi:10.1016/j.jaad.2006.08.016

[2] Brickman WJ, Binns HJ, Jovanovic BD, et al. Acanthosis nigricans: a common finding in overweight youth. Pediatr Dermatol. 2007;24(6):601-606. doi:10.1111/j.1525-1470.2007.00547.x

[3] Kong AS, Williams RL, Smith M, et al. Acanthosis nigricans and diabetes risk factors: prevalence in young persons seen in southwestern US primary care practices. Ann Fam Med. 2007;5(3):202-208. doi:10.1370/afm.678

[4] Torley D, Bellus GA, Munro CS. Genes, growth factors and acanthosis nigricans. Br J Dermatol. 2002;147(6):1096-1101. doi:10.1046/j.1365-2133.2002.05150.x

[5] Kebria MM, Belinson J, Kim R, Mekhail TM. Malignant acanthosis nigricans, tripe palms and the sign of Leser-Tre'lat, a hint to the diagnosis of early stage ovarian cancer: a case report and review of the literature. Gynecol Oncol. 2006;101(2):353-355. doi:10.1016/j.ygyno.2005.12.024

[6] Yeh JS, Munn SE, Plunkett TA, Harper PG, Hopster DJ, du Vivier AW. Coexistence of acanthosis nigricans and the sign of Leser-Trélat in a patient with gastric adenocarcinoma: a case report and literature review. J Am Acad Dermatol. 2000;42(2 Pt 2):357-362. doi:10.1016/s0190-9622(00)90112-9

[7] Huang Y, Hessami-Booshehri M. Acanthosis nigricans at sites of insulin injection in a man with diabetes. CMAJ. 2018;190(47):E1390. doi:10.1503/cmaj.180705

[8] Schwartz RA. Acanthosis nigricans. J Am Acad Dermatol. 1994;31(1):1-22. doi:10.1016/s0190-9622(94)70128-8

[9] Schmidt TH, Khanijow K, Cedars MI, et al. Cutaneous Findings and Systemic Associations in Women With Polycystic Ovary Syndrome. JAMA Dermatol. 2016;152(4):391-398. doi:10.1001/jamadermatol.2015.4498

[10] Yılmaz E, Kelekci KH, Kelekci S. Skin tag and acanthosis nigricans: do they have a predictive value for gestational diabetes mellitus?. Exp Clin Endocrinol Diabetes. 2011;119(7):419-422. doi:10.1055/s-0030-1270478

Author: Doctor Fei Dao Duan Yu

Review | Xu Min, deputy chief physician of the Department of Dermatology, Zhu Xianyi Memorial Hospital, Tianjin Medical University