What is Prurigo Pigmentosa?
Prurigo pigmentosa
nagashima disease and also known as 'keto rash'.
Who gets prurigo
pigmentosa?
Prurigo pigmentosa
has been described in people of all ages, genders and ethnicities. However, it
is more common among Asians, especially among young women. Women are generally
twice as likely to be infected as men.
It has been
increasingly associated with ketotic conditions associated with diabetes,
fasting and post-bariatric surgery.
In some patients, prurigo pigmentosa is associated with systemic disorders such as eating disorders such as Sjogren's syndrome and anorexia nervosa. It has been described in people with atopy as well as in pregnancy.
What causes prurigo
pigmentosa?
The exact role of
carbohydrate and ketosis exclusion in the development of prurigo pigmentosa has
not yet been elucidated.
Several other
procedures have been proposed for Prurigo Pigmentosa, including allergy to
clothing or contact with trichlorophenol, chromium in acupuncture needles,
chrome in detergent, and nickel.
How does Prurigo pigmentosa appear?
Clinical features
of Prurigo pigmentosa are:
A pruritic (itchy) rash, which may recur
Swollen, red raised
spots (papules) that come together to form a lattice (network-like) pattern
Symmetrical
distribution in the trunk often affects the upper back, sacrum (birthmarks),
abdomen, and chest.
Rare involvement of
mouth or limbs
Damage to mucous
membranes, hair and nails
Reticulated
hyperpigmented patches after resolution of the inflammatory phase of the rash.
Histopathology of
prurigo pigmentosa
Prurigo pigmentosa
has distinct histopathology.
Early lesions:
dorsal perivascular neutrophilic penetration, and a few necrotic keratinocytes
Developed lesions:
patchy lymphocytic infiltration, and necrosis of numerous keratinocytes
Late lesions:
lymphocytic infiltration, scale-crust, and melanoma
What is the
treatment for prurigo pigmentosa?
Adding carbohydrates
to the diet can be beneficial if the patient follows a ketogenic diet or fasts
for a long time or has abdominal surgery.
Dapsone and
tetracycline antibiotics are effective in treating prurigo pigmentosa in the
inflammatory stage of the disease. These therapies are thought to work by
interfering with the movement and efficacy of neutrophils. Recently macrolide
antibiotics such as erythromycin have also been shown to be helpful. It is not
clear whether the antibacterial action of the antibiotic is relevant.
Topical and
systemic corticosteroids are not effective for prurigo pigmentosa.
To date, there is no effective treatment for hyperpigmentation that develops in the later stages of the disease. It eventually fades.
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