|Synonyms||Mongolian blue spot, congenital dermal melanocytosis, dermal melanocytosis|
|Mongolian spot visible on six-month-old Taiwanese baby girl|
|Classification and external resources|
|ICD-10||D22.5 (ILDS D22.505)|
|ICD-9-CM||757.33 (CDC/BPA 757.386)|
Mongolian spot (congenital dermal melanocytosis) are birthmarks that are present at birth and the most commonly located in the sacrococcygeal or lumbar area.  Lesions may be single or multiple and usually involve <5% total body surface area. They are macular and round, oval or irregular in shape. The color varies from blue to greenish, gray, black or a combinations of any of the above.  The size varies from few to more than 20 centimeters.  Pigmentation is most intense at the age of one year and gradually fades thereafter. It is rarely seen after the age of 6 years. 
Historical and anthropological perspective
The earliest known accounts of Mongolian spots date back to Hippocrates, who believed that a blow to the pregnant mother's abdomen manifests as a mark at the corresponding place in the newborn. A similar theory also prevailed in Turkey, where it was known as 'leek' or 'spot'. Father Gumilla was the first Westerner to describe Mongolian spots in his writings. The Mongolian spot is referred to in Japanese as 'asshirigaaoi', meaning to have a blue bottom, and it believed to be the consequence of coitus performed during pregnancy, or a mark made by the gods presiding over births. In China, it is known simply as 'taiji' which means a mark, where, when a child is born, God gives it a 'spank' to give it a start in life. According to one legend, the 'King of the Underworld' slaps the child to make it come out. This is reflected in the Mexican term for Mongolian spots, 'la patada de Cuahetemoc', meaning Cuahetemoc's kick. According to Armenian superstition, if a woman works on certain days or if another woman criticizes her and places her hand on the abdomen, then the child is born with this mark or ibid at that spot. It was German professor Edwin Baelz who, in 1885, described it in Mongolians and named it 'Mongolian Flecke' or Mongolian spot. Baelz believed that Mongolian spots were a distinct characteristic of the Mongols and other non-caucasian races.
Mongolian spots, or Dermal melanocytosis, result from failure of complete melanocyte migration into the epidermis before birth with ensuing dermal nesting and melanin production. If there are many spots, or a spot covers a large area, it may be a sign of an underlying disorder, such as a metabolism problem called GM1 gangliosidosis Type 1. Recent data suggest that Mongolian spots may be associated with inborn errors of metabolism.  Inborn errors of metabolism arise from single gene defect, most often involving an enzyme function, which leads to disruption of a specific metabolic pathway giving rise to abnormalities in the synthesis or catabolism or proteins, fats or carbohydrates.  The most common condition associated with Mongolian spots is Hurler's disease followed by GM1 gangliosidosis Type 1. The clinical manifestations in Mongolian spots in inborn errors of metabolism are spots deeper in color and have a generalized distribution involving dorsal and ventral trunk in addition to sacral region and extremities. They are persistent and in some cases an indistinct feathery border has been described. The majority of the neonatal cutaneous lesions are physiological and transient requiring no therapy.  It is necessary to differentiate between benign and clinically significant skin lesions in newborn. Therefore, it is important to be aware of the innocent transient skin lesions in newborn and differentiate these from other serious conditions, which will help avoid unnecessary therapy to the neonates. Parents can be assured of good prognosis of these skin manifestations. 
Diagnosis is made primarily through physical assessment of the skin, family history of Mongolian spots, and subjective data given by the care giver. No tests are required for diagnosing Mongolian spots.
Males and Females get Mongolian spots equally. A hospital-based, cross-sectional, prospective study was conducted in the Department of Dermatology, Venereology and Leprosy, BLDE University, Shri B. M. Patil Medical College Hospital and Research Center, Bijapur. One thousand neonates delivered in the Department of Obstetrics and Gynecology of the same institution was surveyed for the presence of skin lesions. The study was conducted in the period of November 2007 to May 2009. The study showed that 467 males were born with Mongolian spots and 380 females were born with Mongolian spots. The results showed there was no statistical significance in males and females born with Mongolian spots. Within the same study, different racial groups were recorded and documented. The study showed that among the Australian neonate, 25.5% were born with Mongolian spots. In the Iranian neonate, 71-81% were reported, in the Japanese neonate 81.5%, in the Turkish neonate 13.2%, in the caucasian neonate 62.8%, in the African American neonate 86.6%, and in the Indian neonate 72-89% were reported in having Mongolian spots. The populations with the most incidences of Mongolian spots were Iranian, Japanese, African American, and Indian.
Mongolian spots usually resolve by early childhood and hence no treatment is generally needed if they are located in the sacral area. However, sometimes it may be required for extra sacral lesions to have surgical correction. Q-switched alexandrite lasers have been used for treatment.  Good results are obtained if treatment is initiated before the age of 20 years. In a study done by the University of Tokyo, the effectiveness of the Q-switched alexandrite laser in treating Mongolian spots was evaluated.  A retrospective study was done from April 2003 to September 2011. 16 patients, aged 14-55, were treated with Q-switched alexandrite laser. A good therapeutic outcome was achieved on the whole group, however two patients with sacral Mongolian spots suffered from inflammatory hyperpigmentation, and two patients got post inflammatory hypopigmentation after seven sessions of laser treatment.
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