On the natural history and comparative pathology of the blue naevus.

This article explores the nature and pathology of the blue naevus condition in humans, in comparison with similar conditions in animals. It provides observations from unique human and animal cases to argue that this could be a neurochristic disorder involving the head segments and skin cells producing color (melanocytes).

Overview of Blue Naevus

• The paper discusses the blue naevus, which is the most common anomaly related to the distribution of melanocytes in human dermis (skin).
• Melanocytes are cells that produce color and originate from the neural crest, a group of transitory cells that play various roles during embryologic development.
• For most part, these cells reach the epidermis, the outermost layer of skin. However, in some conditions, such as a blue naevus, they may be found in the dermis.

Comparative Pathology

• The research draws comparisons between the blue naevus in humans and similar conditions in other animals.
• The common melanocytoma in dogs and hamsters, for instance, is equated to the blue naevus in humans.
• The paper further elaborates on comparing the human blue naevus to more widespread dermal melanocytoses in animals. Again, more extensive dermal melanocytoses are rare in humans.

Unique Cases and Theory

• The author shares a unique human case where an individual died from melanoma after extensive dermal melanocytosis, drawing parallels between this condition and a similar disorder occurring in aging, greying horses known as equine melanotic disease.
• The author argues that these conditions could be examples of a neurochristic disorder. Neurochristic disorders are conditions involving cells from the neural crest that have migrated to abnormal locations during development.
• Both conditions involve the melanocytes from the head (cephalad) segments and seem to resemble the neural crest cell disorder role in the genesis of the conditions.