A 2-day-old infant boy who was born with large, ill-defined, blue-gray hyperpigmented patches on his posterior trunk and sacral area presents. The child’s parents are healthy and have no medical problems. No one in the child’s family has had similar dermatologic findings. The pregnancy was normal and the child was born without complications. The infant has been eating and sleeping well and has no concerning signs or symptoms of systemic disease.
A 4-day-old infant boy who was born with a large, well-defined brown-black hyperpigmented patch on his posterior trunk presents. There are several smaller satellite brown macules around the large brown patch. The child’s parents are healthy and have no medical problems. No one in the child’s family has had similar dermatologic findings. The pregnancy was normal and the child was born without complications. The infant has been eating and sleeping well and currently has no concerning signs or symptoms of systemic disease.
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Congenital dermal melanocytosis (CDM), also known colloquially as Mongolian spots, are benign lesions present at birth as blue or blue-gray patches on the skin; they typically resolve within the first few years of life.1-2
CDM affects boys and girls equally; however, prevalence varies greatly with race and the population sampled. Asian and African populations are the most commonly affected, with some studies showing a frequency of 100%.1 White populations are the least commonly affected.3 Although the lumbosacral region is the most common location of presentation, other locations, including the shoulders, hands, and thighs, have been reported.3
Dermal melanocytosis results from the abnormal persistence of melanocytes in the dermis after the 20th week of embryologic development. In normal development, melanocytes differentiate from neural crest cells and form in the dermis at the 10th week of gestation; in all locations, except for the scalp, sacrum, and extensor surfaces of the extremities, these melanocytes then either move into the epidermis or are removed by macrophages.1,3 CDM appears blue due to the increased dermal reflection of short wavelengths of light, called the Tyndall effect.1,3 Persistence of CDM past the first few years of life can be due to a protective sheath surrounding melanocytes or the presence of growth factors in the dermis that support melanocyte growth.3,4 Associated risk factors for the development of CDM include drug use by the pregnant mother and premature birth.5
Clinically, CDM presents as a single, blue-green, irregularly shaped spot, smaller than 5 cm, at the sacrum.5 In rare cases, there are multiple spots, spots greater than 10 cm in size, oval and linear shapes, spots of varying colors, and lesions located across the body.5 CDM can be clinically classified based on the age of spot regression; the common type, extensive type, and persistent type regress early in childhood, later in childhood, and after childhood, respectively.3 Most spots (57%) resolve or start to regress by age 1 year.5 CDM is benign, but extensive involvement can be associated with many conditions, including metabolic disorders, cleft lip and palate, mucopolysaccharidosis, and lysosomal storage diseases.3,4 Histologically, collagen bundles intermixed with abnormal dendritic melanocytes are seen in the lower half or two-thirds of the dermis, where melanocytes are not normally present.1,4 These melanocytes are spindle or pear-shaped, and they are small enough that they do not disrupt the normal structure of the dermis.1-3
The differential diagnosis of CDM includes other congenital lesions, including congenital melanocytic nevus (CMN), nevus of Ota, nevus of Ito, Hori nevus, ecchymosis, and child abuse.1-3 CMN is a tan or dark spot of hyperpigmentation present at birth; it is differentiated from CDM by its brown color and frequent association with overlying hypertrichosis.1 Nevus of Ota and nevus of Ito present before age 1 year or near puberty as blue or brown patches on the skin on the face, specifically within the dermatomal distributions of the ophthalmic and maxillary branches of the trigeminal nerve and the supraclavicular/deltoid region, respectively.1 These conditions do not spontaneously regress and rarely can undergo malignant transformation. Although similar in color, CDM is differentiated from nevus of Ota and nevus of Ito by its location, time of onset, and early regression.2-3 Hori nevus consists of brown- or gray-colored skin patches that develop during adulthood and most commonly affect the face.1 The onset of presentation and location of hyperpigmentation thus distinguish CDM from Hori nevus. In rare cases, bruises from child abuse can mimic CDM and are excluded from the differential if the lesions are nontender, maintain their color, and regress over the course of months.3
Because the lesions most commonly regress with normal aging, particularly those in the sacral region, no treatment is usually needed.3 For small lesions that cause psychosocial distress, cosmetic masking agents can be used.1,3 A Q-switched alexandrite or ruby laser effectively treats most lesions, although some patients experience residual hyper- or hypopigmentation.6-7 Treatment before age 20 years and administration of bleaching creams before treatment can improve outcomes and reduce postlaser pigmentation.3,4
In our case, the parents of the patient were reassured that the lesion was benign and would most likely resolve with age.
Congenital melanocytic nevi (CMN) occur at birth or soon after and are variable in size, but generally appear as round or oval, slightly raised or flat brown lesions on the trunk, legs and arms, head and neck, and extremities.1,8-10 There may be associated hypertrichosis, hyperkeratosis, erosions, or ulcerations.11 Multiple congenital nevi are seen in 3% of patients.8,11-12
The physical appearance of congenital nevi may change over time, with thickening, changes in texture, or development of papules and nodules within the lesion.8 CMN are classified by projected adult size, with small, medium, and giant nevi described as less than 1.5 cm in diameter, between 1.5 and 19.9 cm, and greater than 20 cm, respectively.1,8
The prevalence of congenital nevi is variable. Small- and medium-sized congenital nevi have an incidence of approximately 1%, whereas giant congenital nevi are more infrequent, with an incidence of 0.005% or less.1,4,8 African and Japanese populations are more commonly affected than Hispanic or white populations, and girls and women are more commonly affected than boys and men.8
Giant congenital nevi, specifically, are most commonly located on the posterior trunk, often have smaller satellite nevi distributed throughout the body and are associated with an increased risk of melanoma.1,8-12 Whereas patients with small- or medium-sized congenital nevi have no increased risk for development of melanoma, patients with giant congenital nevi have a 5-year risk for melanoma of 4.5%.1 Approximately 60% of melanomas in patients with giant congenital nevi develop within 10 years after birth.4 CMN are associated with many more malignant conditions8; thus, suspicious lesions arising within CMN should be biopsied and evaluated to rule out malignancy.
Another concern in patients with giant congenital nevi, particularly those in an axial location with multiple satellite lesions, is neurocutaneous melanosis. This condition is characterized by CMN associated with meningeal melanosis or melanoma. Magnetic resonance imaging (MRI) should be performed if risk factors or symptoms of increased intracranial pressure are present.
Congenital nevi arise from melanocytes and develop between 40 days and 6 months of gestation.1 Although the exact etiology is unknown, there is an established association between congenital nevi and NRAS mutations; however, results of studies on familial inheritance are inconsistent.1,8,9 Unlike acquired nevi, congenital nevi lack BRAF mutations.1,8
There are no definitive histologic criteria for congenital nevi. Congenital nevus cells are found in the lower reticular dermis, subcutaneous fascia, and deeper.1,4 Histologic diagnosis can be difficult because congenital nevi cells show identical features to normal acquired nevi.1,10 Congenital nevi cells often extend in a linear pattern or between collagen bundles, and involve blood vessels, hair follicles, sweat glands, arrector pili, and cutaneous nerves, which can support the diagnosis.1,4,8,10
CMN are fairly easy to diagnose when seen at birth. Other congenital birthmarks, including hemangiomas and dermal melanocytosis, are distinguished by clinical appearance. Becker nevus is a pigmented patch on the upper trunk and proximal extremities that most commonly appears during childhood or adolescence.1 During puberty, the lesion can undergo thickening and darkening and develop overlying hypertrichosis. Its location and clinical history help differentiate this lesion from CMN.
Another differential diagnosis of CMN is plexiform neurofibroma. This lesion, pathognomonic for neurofibromatosis, is a proliferation of nerves that becomes apparent in early childhood; it presents as a soft subcutaneous nodule or plaque, sometimes with overlying hyperpigmentation and hypertrichosis. Other findings of neurofibromatosis, the soft and boggy texture, and histologic diagnosis of plexiform neurofibroma aid in differentiation.
The decision to remove a nevus can be based on a patient’s risk for developing melanoma, and the size, location, and cosmetic appearance of the nevus.1 The treatment for most small- and medium-sized CMN is yearly monitoring, given the low risk for development of melanoma. Removal of the entire nevus has been shown to improve patient satisfaction for nevi smaller than 20 cm but may not improve the risk for cancer development when compared with a partial removal.13 For large congenital nevi, delaying surgery until 6 months after birth is the preferred treatment for high-risk patients, but the risks of anesthesia and location of the nevus must be weighed.1,4,11 Dermabrasion, curettage, and lasers have all been used as alternative treatments for congenital nevi by reducing the elevation and pigmentation; however, these treatments do not decrease cancer risk.1 In all cases of CMN, the risk for scarring, deformities, or decreased quality of life should be considered.13
In our case, due to the size of the nevus, MRI was ordered, and the patient was referred to a pediatric dermatology specialist. MRI was ordered to rule out possible neurocutaneous melanosis, which has been associated with giant axial congenital nevi. The patient will be routinely followed to screen for the development of melanoma within or outside the lesion.
Austin Jones, BS, is a medical student and Connie Wang, MD, is a dermatology resident at Baylor College of Medicine in Houston. David Rizk, BA, is a medical student at the University of South Alabama in Mobile.
- Bolognia JL, Jorizzo JL, Schaffer JZ. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012.
- Cordova A. The Mongolian spot: a study of ethnic differences and a literature review. Clin Pediatr (Phila). 1981;20:714-719.
- Gupta D, Thappa DM. Mongolian spots. Indian J Dermatol Venereol Leprol. 2013;79:469-478.
- James WD, Berger TG, Elston DM, Neuhaus IM. Andrews’ Diseases of the Skin: Clinical Dermatology. 12th ed. Philadelphia, PA: Elsevier; 2016.
- Gupta D, Thappa DM. Mongolian spots—a prospective study. Pediatr Dermatol. 2013;30:683-688.
- Kagami S, Asahina A, Uwajima Y, et al. Treatment of persistent Mongolian spots with Q-switched alexandrite laser. Lasers Med Sci. 2012;27:1229-1232.
- Shirakawa M, Ozawa T, Ohasi N, Ishii M, Harada T. Comparison of regional efficacy and complications in the treatment of aberrant Mongolian spots with the Q-switched ruby laser. J Cosmet Laser Ther. 2010;12:138-142.
- Alikhan A, Ibrahimi OA, Eisen DB. Congenital melanocytic nevi: where are we now? Part I. Clinical presentation, epidemiology, pathogenesis, histology, malignant transformation, and neurocutaneous melanosis. J Am Acad Dermatol. 2012;67:495.e1-495.e17.
- Chitsazan A, Ferguson B, Ram R, et al. A mutation in the Cdon gene potentiates congenital nevus development mediated by NRAS (Q61K). Pigment Cell Melanoma Res. 2016;29:459-464.
- Tannous ZS, Mihm MC Jr, Sober AJ, Duncan LM. Congenital melanocytic nevi: clinical and histopathologic features, risk of melanoma, and clinical management. J Am Acad Dermatol. 2005;52:197-203.
- Lyon VB. Congenital melanocytic nevi. Pediatr Clin North Am. 2010;57:1155-1176.
- Zayour M, Lazova R. Congenital melanocytic nevi. Clin Lab Med. 2011;31:267-280.
- Ibrahimi OA, Alikhan A, Eisen DB. Congenital melanocytic nevi: where are we now? Part II. Treatment options and approach to treatment. J Am Acad Dermatol. 2012;67:515.e1-515.e13.