A 4-week-old boy is brought to the office for his first well-child visit. The patient was born at 38 weeks gestation to a 27-year-old woman following an uncomplicated pregnancy and delivery. He has been exclusively breast-fed since birth and has had normal urine and stool output. The patient takes supplemental vitamin D and no other medications. His 4-year-old brother has neurofibromatosis but is otherwise healthy. The patient is well-appearing and vigorous. His weight and length are at the 50th percentile. There is a 5-cm skin lesion with overlying hair on the upper back, as shown below. The remainder of the skin examination is unremarkable. Which of the following is the most likely diagnosis for this patient?

Question

A 4-week-old boy is brought to the office for his first well-child visit.  The patient was born at 38 weeks gestation to a 27-year-old woman following an uncomplicated pregnancy and delivery.  He has been exclusively breast-fed since birth and has had normal urine and stool output.  The patient takes supplemental vitamin D and no other medications.  His 4-year-old brother has neurofibromatosis but is otherwise healthy.  The patient is well-appearing and vigorous.  His weight and length are at the 50th percentile.  There is a 5-cm skin lesion with overlying hair on the upper back, as shown below.  The remainder of the skin examination is unremarkable.  Which of the following is the most likely diagnosis for this patient?

Quizplus · Accepted Answer

11ec25c8_d649_08a7_bc81_f38bf8fd7fee_MD0003_00 This patient has a congenital melanocytic nevus (CMN), a benign proliferation of melanocyte cells. CMNs present within the first few months of life and are usually solitary, hyperpigmented lesions with an increased density of overlying dark, coarse hairs. Initially presenting with flat homogenous hyperpigmentation, CMNs can grow during infancy and appear as heterogeneously pigmented and raised. The risk of transformation to melanoma increases (up to 5%) with increasing size of a CMN, and large lesions are often removed surgically to reduce risk. Small lesions may be removed for cosmetic reasons given their low risk of melanoma transformation. (Choice A) Café au lait macules are flat, hyperpigmented lesions that can be isolated or associated with McCune-Albright syndrome or neurofibromatosis. This patient's presentation of a hyperpigmented lesion with overlying dense hairs is not consistent with a café au lait macule. Café au lait macules (Choice B) Congenital dermal melanocytosis (Mongolian spots) presents as flat, gray-blue patches that are poorly circumscribed and will fade with time. They are classically located on the lower back and sacrum, and are more common in Asian and African American populations. (Choices D and E) Nevus simplex and nevus flammeus are flat, blanchable, and erythematous vascular birthmarks. Nevus simplex lesions are typically located on the eyelids, glabella, and nape of the neck and fade with time; nevus flammeus lesions (port-wine stains) do not regress with time and are usually unilaterally located on the face. Nevus simplex and nevus flammeus (Choice F) Infantile hemangiomas are bright red, raised plaques that can occur anywhere on the body. They typically proliferate in the first year of life and involute over subsequent years. Infantile hemangiomas Educational objective: A congenital melanocytic nevus presents within the first few months of life as isolated hyperpigmented patches with an increased density of hair follicles. References: Congenital melanocytic nevi: where are we now? Part I. Clinical presentation, epidemiology, pathogenesis, histology, malignant transformation, and neurocutaneous melanosis. (http://www.ncbi.nlm.nih.gov/pubmed/22980258)

A 4-Week-Old Boy Is Brought to the Office for His