A 22-year-old single female presented to primary care Wazarat Health Center at Prince Sultan Military Medical City in Riyadh, with a 3 weeks history of itchy erythematous papules and vesicles and papulo-vesicles over the neck, chest, and upper back and face, which started 4 to 5 days after bariatric surgery. The patient on daily multivitamin supplements, vitamin D (50,000 IU, weekly / 2 months). The patient has lost 4kg since the operation, family history of atopy was positive regarding the mother physical examination shows erythematous papules and vesicles and papulo-vesicles over the neck with crust, chest, and upper back,

Based on medical history and clinical presentation a provisional diagnosis was Prurigo Pigmentosa. The patient was prescribed topical mometasone furoate cream (BID for one week). Two -week follow-up showed improvement of the eruption.

The course of the disease was shorter than usual in such cases the patient response to treatment was reactive to the topical mometasone without taking the oral minocyline, which major of such cases need in the late course of the disease

The patient starts to improve within 2 weeks compared to others who need an average of 6 weeks to improve in such cases

Prurigo pigmentosa is a rare autoinflammatory skin disease that presents with pruritic erythematous papules, vesicles, papulo-vesicles in the back, chest, or neck (figure 1 ) an Early-stage disease is characterized by a superficial perivascular (figure 2) infiltrate of neutrophils; spongiosis and necrotic keratinocytes [1]

Figure 1: chest, multiple erythematous reticulated papules and plaques, and vesicles with post-inflammatory hyperpigmentation.

Figure 2: multiple erythematous reticulated and crusted papules and plaques with hyperpigmented macules and patches.

Prurigo Pigmentosa has no clear pathogenesis [1]. Recent literature shows an increasing association link between Prurigo pigmentosa and bariatric surgery, also associated with ketosis because of metabolic disturbances as a result of such procedure [2]. Increased physician awareness about post-bariatric Prurigo Pigmentosa is very important especially with the growing popularity of bariatric surgery and weight reduction procedures and diet.

The First report of Prurigo Pigmentosa was in 1971 by Nagashima et al [3], more than 300 cases Prurigo Pigmentosa have been reported [7]. The female-to-male ratio 6:1, which more affecting the Japanese and East-Asian populations (5) Last year's increased cases of Prurigo Pigmentosa in Western countries, and recently, in the Middle East [2].

The causes of Prurigo Pigmentosa is not clear but a metabolic disturbance which is associated with multiple conditions such as diabetes mellitus, fasting/diet, pregnancy, atopy, and being in a ketotic state and bariatric surgery which become more popular nowadays seen as a result of such procedure [1]

Prurigo Pigmentosa is associated with systemic diseases such as Sjegoren disease and eating disorders such as anorexia nervosa [6], and some physical factors (skin friction, trauma, acupuncture) [4]

Pathogenesis of Prurigo Pigmentosa is an inflammation-mediated by neutrophils, which make it responding well to medications that have an antineutrophil effect, such as tetracyclines, which would support this neutrophil-mediated theory. Another hypothesis explains the cause of Prurigo Pigmentosa which is a decrease in insulin levels, as reported after bariatric surgery [4].

Oral minocycline is first-line therapy may be indicated for some patient commonly in later stages. [1] Tetracycline antibiotics have been the gold standard treatment of Prurigo Pigmentosa, due to its anti-inflammatory effect on neutrophilic function [8]. Other medications such as macrolide antibiotics, dapsone, potassium iodide, or low-dose isotretinoin have also been used, with different efficacy. Topical and systemic corticosteroids and antihistamines have a limited role in the treatment of Prurigo Pigmentosa [5]. Resumption of normal diet and improvement of oral intake in cases of ketosis was also found to be helpful in the treatment of the disease [3]

As we saw in previous literature the association between Prurigo Pigmentosa and bariatric surgery and the start of symptoms  [2], which were typically similar in our patient starts within 3- 5 days.

Most of the cases present typically in the back and chest and trunk

Which was seen in our patient with involvement in cheeks witch is rare as in the literature [1]

The patient improved with local treatment without the need to start the oral minocycline which is different to such cases [8]

It’s case of Prurigo Pigmentosa post Bariatric surgery with a different response of treatment, and there was no need for minocycline which happens in some cases of Prurigo Pigmentosa , with better response to treatment with topical mometasone, And improved within 2 weeks compared to average  6 weeks as reported in the literature.