Differential Dx includes infectious diseases
The differential includes the following:
- Hansen’s disease (leprosy), caused by Mycobacterium leprae, presents with a loss of sensation at the site of hypopigmentation. This loss of sensation is due to nerve involvement. Histopathology yields a very specific pattern of epithelioid cell granulomas around the dermal nerves.7
- Tinea versicolor, caused by Malassezia furfur, has a fine scale on the hypopigmented patch. The lesion fluoresces under a Wood’s lamp, and a potassium hydroxide (KOH) preparation will be positive, revealing the well-known “spaghetti and meatballs” pattern. Hypopigmentation in tinea versicolor results from the inhibition of the enzyme tyrosinase in the melanocytes.7
- Vitiligo results from the complete absence of melanocytes. Vitiligo is rarely present at birth.
- Nevus depigmentosus, also known as nevus achromicus, is a well-demarcated patch of hypopigmentation that tends to occur on the trunk or proximal extremities in a dermatomal pattern (FIGURE 2). It is a true nevus and diascopy will not result in the loss of the border between the hypopigmented patch and surrounding skin.5
FIGURE 2
Don’t be fooled: This is not nevus anemicus
Make the diagnosis based on the exam
The diagnosis of nevus anemicus is made primarily based on the history and exam. A number of techniques aid in confirming the diagnosis and excluding some of the diagnoses mentioned above.
Diascopy results in the loss of the border between nevus anemicus and normal skin.4,5 Anatomic nevi do not demonstrate this loss in border. Shining a Wood’s lamp does not accentuate the lesion, helping to distinguish nevus anemicus from fungal infections that tend to fluoresce.
Neither friction (produced by scratching a line across both the lesion and normal surrounding skin), nor cold or heat application, induces erythema in the involved areas.2 And unlike leprosy, there is no loss of sensation at the site of the hypopigmentation. A biopsy of the lesion is not needed, but would reveal normal histology. Melanocytes are preserved and normally distributed. Electron microscopy, while not needed, would not detect any abnormalities in the vascular structure.4
Nothing to worry about for our patient
Our patient required no treatment. We simply provided her with some information on the benign nature of nevus anemicus. (In addition, we dealt with the moles on her arms that prompted her visit. They turned out to be normal melanocytic nevi.)
We told the patient that if the lesion on her chest bothered her, she could hide it with concealer make-up.1,2 Our patient and her grandmother were happy with the explanation and did not seek further care.
CORRESPONDENCE
Shehnaz Zaman, MD, 420 Elmington Avenue, #417, Nashville, TN 37205; shehnazzaman@gmail.com