Skin Diseases First Described by Japanese Dermatologists. Part 2: Prurigo Pigmentosa
Wednesday, May 11, 2011
Prurigo pigmentosa (PP) is an inflammatory skin disease
characterized by intensely pruritic papules distributed on the
back, neck and chest, leaving gross reticular or net-like
pigmentation that occurs mainly in young women (Figure 1).
Exacerbations and recurrences are the rule. Although more than 200
patients with this condition have been reported, mainly from Japan,
over 40 cases in the literature are from other Asian and Western
countries. Whether PP really has a proclivity for the Japanese or
whether it is just underdiagnosed outside Japan still remains
unclear; however, once you have encountered a patient with PP, you
will remember the case because of its impressive clinical
manifestations, as well as its prompt clinical response to
minocycline or dapsone.
Figure 1. Early lesions (left-hand images)
and late lesions (right-hand images) on the back of two patients
with prurigo pigmentosa.
In this article, we will review the clinical presentation,
histopathology and treatment of patients with PP.
What is PP?
PP was first reported by Professor Nagashima (1929-2010) of
Kyorin University in 1971 in the Japanese Journal of Dermatology as
"a peculiar pruriginous dermatosis with gross reticular
pigmentation".1 His English publication in the Journal
of Dermatology followed in 1978 and coined the novel name of
As illustrated in Figure 2, the sudden onset of erythematous
papules with severe pruritus is noticed initially, developing into
reticular pigmentation that is symmetrically localized on the
trunk. Clinically, diagnoses of dermatitis herpetiformis,
poikiloderma atrophicans vasculare, confluent and reticulated
papillomatosis, reticulate pigmented dermatosis and pigmented
contact dermatitis are excluded by their different symptoms and
clinical courses, as well as different histopathology. As such, PP
is now recognized as a distinct inflammatory disease of the
Figure 2. Typical clinical course of
prurigo pigmentosa. Early pruriginous pruritic papules (top image)
and fully developed skin legions leaving gross reticular
pigmentation (bottom image).
The etiology and pathogenesis of PP still remain unclear;
however, reported causative factors include ethnic predisposition,
environmental causes, seasonal variation, mechanical stimuli (eg,
friction from cloths), contact allergens (eg, chrome and nickel),
and ketosis as a consequence of diabetes mellitus, anorexia nervosa
Histopathology of PP
By studying 25 patients with PP and reviewing 178 cases in the
literature, Boer and Ackerman6 reported that
histopathological changes transpire rapidly, as do the clinical
features throughout the entire disease course. Although most papers
in the literature have described the histopathology as merely
non-specific lichenoid dermatitis, PP involves dynamic changes from
superficial perivascular dermatitis, spongiotic dermatitis, and
lichenoid dermatitis to post-inflammatory hyperpigmentation,
depending on the stage of the skin lesions.4
Importantly, neutrophils are found in early lesions of PP, as shown
in Figure 3, which may explain why dapsone and minocycline are
effective in the early stages, but ineffective in the late
post-inflammatory pigmentation stage, of PP.6
Figure 3. Neutrophils are scattered in the
papillary dermis in early skin lesions of prurigo
Treatment of PP
Oral/topical corticosteroids and oral antihistamines are usually
ineffective against PP. As most patients have usually been
diagnosed with contact dermatitis or acute prurigo, and have
received topical corticosteroids as well as antihistamines, they
usually complain of a poor response to treatment.
Upon oral administration of minocycline or dapsone, pruritus
will begin to be reduced within 24 h, and the clinical symptoms of
PP will resolve completely if these drugs are given in the early
stages of the disease. This success is so impressive that both
patients and dermatologists will never forget such a case, even if
experienced only once.
Regarding the mechanism of action of these drugs, it is thought
that anti-inflammatory actions, through inhibition of the migration
and/or function of neutrophils, may be responsible, because both
minocycline and dapsone have been reported to modify neutrophilic
functions, such as the generation of neutrophil-derived reactive
oxygen species.7,8 Doxycycline and other sulfonamides
are also effective, presumably because of their similar mechanism
Although PP is a rare inflammatory skin disease, it is not
uncommon, even in non-Asian populations.10,11 It has
highly characteristic clinical manifestations and responds well to
appropriate treatment if a correct diagnosis is made. Increased
recognition of this entity by the Western dermatologic community
will greatly help in improving outcomes of patients with this
- Nagashima M, Ohshio A, Shimizu N. A peculiar pruriginous
dermatosis with gross reticular pigmentation [Japanese]. Jpn J
- Nagashima M. Prurigo pigmentosa - clinical observations of our
14 cases. J Dermatol 1978;5:61-67.
- Joyce AP, Horn T, Anhalt GJ. Prurigo pigmentosa. Arch
- Boer A, Misago N, Wolter M, et al. Prurigo pigmentosa:
A distinctive inflammatory disease of the skin. Am J
- Lu PH, Hui RC, Yang LC, et al. Prurigo pigmentosa: a
clinicopathological study and analysis of associated factors.
Int J Dermatol 2011;50:36-43.
- Boer A, Ackerman AB. Prurigo pigmentosa is distinctive
histopathologiaclly. Int J Dermatol
- Miyachi Y, Niwa Y. Effects of potassium iodide, colchicine and
dapsone on the generation of polymorphonuclear leukocyte-derived
oxygen intermediates. Br J Dermatol
- Miyachi Y, Yoshioka A, Imamura S, et al. Effect of
antibiotics on the generation of reactive oxygen species. J
Invest Dermatol 1986;86:449-453.
- Miyachi Y, Yoshioka A, Horio T, et al. Prurigo
pigmentosa: A possible mechanism of action of sulfonamides.
- Baykal C, Buyukbabani N, Akinturk S, et al. Prurigo
pigmentosa: not an uncommon disease in the Turkish population.
Int J Dermatol 2006;45:1164-1168.
- Boer A, Asgari. Prurigo pigmentosa: An underdiagnosed disease?
Ind J Dermatol Venereol Leprol