To the editor
Interactive quizzes are one of the components of Derm101 (www.derm101.com), a website that hosts many educational resources, including the journal Dermatopathology: Practical and Conceptual. At this time, there are more than 800 quizzes on the website.
The authors of Quiz 649 posted the case of a man with two somewhat nummular patches of hyperpigmentation on the upper back (Fig. 1A), which on biopsy showed melanophages around venules of the superficial plexus and in dermal papillae (Fig. 1B).The authors diagnosed the findings in this case as postinflammatory hyperpigmentation. But, on reviewing the images of this quiz, I think that the best diagnosis in this case is notalgia paresthetica.
Fig. 1A and B
Fig. 1A and B. Clinical appearance and histopathology of the case presented as quiz number 649. Reproduced from “Interactive Quizzes,” available at: www.derm101.com
First defined by Astvatsaturov in 1934,  notalgia paresthetica (NP) is a primary sensory neuropathy of unknown cause affecting the second to the sixth thoracic spinal nerves.  The characteristic symptom is pruritus on the back occasionally accompanied by pain, paresthesia, or hyperesthesia. The dermatologic finding consists of a well-circumscribed hyperpigmented patch and is thought to be the result of chronic rubbing and scratching that follows the pruritus.  A skin biopsy in NP may show intraepithelial necrotic keratinocytes with melanin and melanophages in the papillary and mid dermis, [2,3] and there is no specific pathological feature. However, some authors observed a significant increase in the number of dermal nerves in a case of notalgia paresthetica. Immunohistochemical examination using a neural marker, S-100, positively stained the nerves. Interestingly, a biopsy from perilesional skin also showed an abnormal nerve proliferation. 
No definite treatment has been found for this disorder and most of the cases reported to date are anecdotal. Topical capsaicin is the option used most widely among dermatologists. Transcutaneous electrical nerve stimulation, gabapentin, oxcarbazepine , botulinum toxin and Ultraviolet B have recently shown promising effects. 
In short, I emphasize the importance of clinicopathological correlation in reaching a more precise diagnosis in this case.
Khalid Al Aboud, M.D., is a dermatologist at the Department of Dermatology, King Faisal Hospital, Makkah, Saudi Arabia. Contact author via email: firstname.lastname@example.org.
- Savka E, Bolukbasib O, Akyolb A, Karamana G. Open pilot study on oxcarbazepine for the treatment of nostalgia paresthetica. J Am Acad Dermatol. 2001;45(4):630-32.
- Goulden V, Toomey PJ, Highet AS. Successful treatment of nostalgia paresthetica with a paravertebral local anesthetic block. J Am Acad Dermatol. 1998;38(1):114-16.
- Weber PJ, Poulos EG. Notalgia paresthetica. Case reports and histologic appraisal. J Am Acad Dermaol. 1988;18(1):25-30.
- Inaloz HS, Kirtak N, Erguven HG, et al. Notalgia paresthetica with a significant increase in the number of intradermal nerves. J Dermatol 2002;29(11):739-43.
- Perez-Perez L. Allegue F, Fabeiro JM, Caeiro JL, Zulaica A. Notalgia paresthetica successfully treated with narrow-band UVB: report of five cases. J Eur Acad Dermatol Venereol. 2010;24(6):730-32.
Reply by Thiago Jeunon, M.D., and Masoud Asgari, M.D.
Postinflammatory pigmentation is still the best and correct answer for Quiz 649
The Interactive Quizzes on www.derm101.com are a teaching tool based on diagnosis of skin lesions through morphologic criteria, both clinically and histopathologically. As a rule, there is little, if any, information about symptoms, and readers are invited to make the diagnosis of dermatologic conditions without the benefit of anamnesis.
Dr. A. Bernard Ackerman was the major author of the first 805 Quizzes, including Quiz 649 posted in 2007. Dr. Al Aboud argues against the diagnosis of postinflammatory pigmentation and states that notalgia paresthetica would be the best and correct answer for this Quiz. In our opinion, this is an overstatement.
Postinflammatory pigmentation is a secondary skin change in which hyperpigmented brown macules come into being. Histopathologically, there are melanophages in the upper dermis and an increase in the amount of melanin in basal keratinocytes, without any evidence of the primary pathological process. This is exactly what was presented in the Quiz in question.
On the other hand, notalgia paresthetica is a sensory nerve entrapment syndrome involving the T2-T6 dermatomes and is characterized by intermittent pruritus, accompanied by pain, tenderness, burning, and heat or cold sensation. [1-6] It is often associated with degenerative changes in vertebra and sometimes related to compression of nerve branches by muscles and fascia. [2-4,6] Most cases of notalgia paresthetica present with postinflammatory pigmentation of the skin in the affected dermatomes secondary to rubbing and scratching. However, some are devoid of any skin lesions. [2,4,6] Nevertheless, postinflammatory pigmentation on the back maybe completely unrelated to notalgia paresthetica, as could be seen, for example, in a healed lesion of fixed drug eruption in this topography. Some authors have found an increased number of nerve fascicles on skin biopsies from patients with notalgia paresthetica,  but these findings have not been reproduced by others. [2,8] In fact, there is no specificity in skin lesions of notalgia paresthetica; all are secondary to chronic rubbing. Therefore, the diagnosis of this syndrome should be based on the assessment of neurologic symptoms and complementary tests directed at them, although hyperpigmented scapular patches may call attention to this possibility.
In sum, the patient presented in Quiz 649 surely has postinflammatory pigmentation on his back. Although an underlying notalgia paresthetica conceptually could be a possibility, confirmation or exclusion of this diagnosis cannot be made in the absence of a compelling history. For this reason, postinflammatory pigmentation still is the only correct answer in this case.
- Yosipovitch G, Samuel L. Neuropathic and psychogenic itch. Dermatol Ther. 2008; 21: 32-41.
- Raison-Peyron N, Meunier L, Acevedo M, Meynadier. Notalgia paresthetica: clinical, physiopathological and therapeutic aspects. A study of 12 cases. J Eur Acad Dermatol Venereol. 1999; 12: 215-221.
- Savk O, Savk E. Investigation of spinal pathology in notalgia paresthetica. J Am Acad Dermatol. 2005; 52 (6): 1085-1087.
- Williams EH, Rosson GD, Elsamanoudi I, Dellon AL. Surgical decompression for notalgia paresthetica: a case report. Microsurgery. 2010, 30: 70-72.
- Misery L. What is nostalgia paresthetica? Dermatology. 2002; 204: 86-87.
- Wang CK, Gowda A, Barad M, Mackey SC, Carroll IR. Serratus muscle stimulation effectively treats notalgia paresthetica caused by long thoracic nerve dysfunction: a case series. J Brachial Plex Peripher Nerve Inj. 2009; 4: 17.
- Inaloz HS, Kirtak N, Erguven HG, Karakok M, Inaloz SS. Notalgia paresthetica with a significant increase in the number of intradermal nerves. J Dermatol. 2002; 29(11): 739-43.
- Savk E, Dikicioglu E, Culhaci N, Karaman G, Sendur N. Immunohistochemical findings in notalgia paresthetica. Dermatology. 2002; 204: 88-93.
Thiago Jeunon, M.D., is from the Department of Dermatology, Bonsucesso Federal Hospital, Rio de Janeiro, Brazil, Masoud Asgari, M.D., is from the Ackerman Academy of Dermatopathology, NY, USA. Both are authors of the Interactive quizzes on derm101.com as of December 2008. Contact corresponding author via email: email@example.com