I haven’t written much about the keto-rash, prurigo pigmentosa lately despite promising that I would (shame on me) so I’ve decided to do a more in depth review of some of the literature that is available.
This article is hot off the presses, just published in the American Journal of Dermatology on July 30, 2014.
Prurigo Pigmentosa: A Clinicopathologic Study of 4 Cases from the Middle East
This was the first case series from the Middle East, out of the American University of Beirut Medical Center, Lebanon.
SUBJECTS:
- All 4 patients were female with a mean age of 23.5
- 3 of the 4 had a history of prior episodes
- One patient reported an association with the rash and with Ramadan fasting.
- Another patient reported that the rash appeared after losing weight as a result of strict dieting over 1 month (approximately 7 kg lost)
- Another patient was also in a diet for weight loss, but the amount lost was not specified
- The last did not report any weight loss or fasting
BIOPSIES:
Biopsies were performed on all 4 patients and characterized using “Boer Criteria”
- 2 biopsies had features of ‘early lesions’
- The differential diagnosis for these was impetiginized spongiotic dermatitis and eruptive psoriasis
- 1 biopsy had features of ‘late lesions’
- Differential diagnosis of chronic spongiotic dermatitis
- 1 biopsy had features of ‘fully developed lesions’
- Differential diagnosis of spongiotic dermatitis or a viral exanthem
TREATMENT:
All 4 responded to treatment and were disease free up to 2 years. Results were apparent within 1-2 weeks
- 1 patient treated with Minocycline 50 mg twice a day for 1 month
- Minocycline as replaced dapsone as preferred therapy because it is safer, more effective, and better in preventing recurrences.
- It also has anti-inflammatory along with the antibiotic effects
- 2 patients treated with Doxycycline 100 mg twice a day for 1 month
- Doxycyline has a better side-effect profile than both minocycline and dapsone
- This also as both anti-inflammatory and antibiotic effects
Interestingly, 1 patient was treated previously with topical corticosteroids and antihistamine medications with only a partial response.
One line that bothered me regarding the treatment was:
Follow-up information was present in all of our patients who showed excellent response to either minocycline or doxycyclie in addition to cessation of fasting or dieting.
So while the patients were all symptom free after 2 years, we can’t tell if that’s because the antibiotics were effective, or if it was because they stopped fasting and dieting!
PATHOPHYSIOLOGY:
Even with this most recent paper they state that the “pathogenesis of PP is not very well understood,” and go on to discuss suspected causes from prior studies including:
- Ketosis – “Ketone bodies may reside around blood vessels and cause perivascular inflammation or enter into cells and modify intracytoplasmic processes.”
- Pregnancy – “Worsening PP during menstruation and pregnancy suggests a possible hormonal role…”
- Infection of Helicobactor pylori
- Infection with Borrelia spirochetes
- Autoimmune disease
They also warn that this is an entity that can be easily overlooked and is “often misdiagnosed as eczema.”