What is the most likely diagnosis for a café au lait spot in a newborn?

Café au lait spots are flat, pigmented skin lesions that can be a common finding in newborns and infants. When multiple café au lait spots are present, they are highly suggestive of underlying conditions such as neurofibromatosis type I (NF1).

In the case of neurofibromatosis type I, café au lait spots are one of the hallmark signs. The presence of six or more café au lait spots, each greater than 5 mm in diameter in prepubertal children, is sufficient for a diagnosis of NF1. The lesions arise from the proliferation of neural crest cells and are associated with a variety of other features, including neurofibromas, learning disabilities, and bone abnormalities.

While acquired melanocytic nevi, ecchymosis, and hemangiomas can be present in infants, they do not typically present as café au lait spots nor are they associated with the same implications regarding a genetic disorder. Acquired melanocytic nevi are generally elevated and pigmented, ecchymosis refers to bruising rather than a pigmented lesion, and hemangiomas are vascular lesions that present differently than café au lait spots.

Therefore, when seeing a café au lait spot in a newborn, especially