Progressive macular hypomelanosis among Egyptian patients: a clinicopathological study

Abstract

Background:Progressive macular hypomelanosis (PMH) is a disease of unclear etiology. Propionbacterium acnes (P. acnes) was claimed to be an etiological factor.Objectives:The purpose of this study was to document the clinicopathological features of PMH in Egyptian patients and to evaluate the therapeutic outcome.Methods:Patients with clinical features of PMH were recruited. Wood’s lamp examination, skin scrapings for fungi, and skin biopsy specimens were obtained. Biopsies were stained with hematoxylin and eosin, PAS, Fontana-Masson, and S100 protein. Patients received either narrow-band UVB (nbUVB) or nbUVB plus daily topical clindamycin 1% and benzoyl peroxide gel 5% (bcUVB). The period of active treatment was 14 weeks followed by a follow-up period of 24 weeks.Results:Twenty-nine patients were included. Microscopic evaluation of skin biopsy specimens showed no significant differences between lesional and normal skin. Fontana-Masson stained sections showed overall reduction of melanin granules in the basal layer of lesional skin only and S100 staining did not detect significant differences in the number of melanocytes in lesional and normal skin. Nearly complete repigmentation was reported in 10 patients treated with bcUVB compared to 9 patients treated with nbUVb with no significant differences between both groups after 14 weeks. Only 2 patients in each group retained the pigmentation and the remaining patients returned to the baseline color before treatment.Conclusions:This study documented the clinicopathological features of PMH among Egyptians. No permanently effective treatment is available. Further studies are needed to prove or disprove the pathogenic role of P. acnes in PMH.

IsCutibacterium(previouslyPropionibacterium)acnesa potential pathogenic factor in the aetiology of the skin disease progressive macular hypomelanosis?

“…Despite independent studies highlighting a strong association of C. acnes with PMH, a number of cases where C. acnes appears absent in lesional skin, as judged by Wood’s lamp examination, histological staining and, in some cases, microbiological culture from skin swabs or biopsies have been reported 6,8,43–44 . It is important, however, to note that a negative Wood’s lamp result does not confirm that C. acnes is absent, only that levels are below the density detection limit (~10 3 organisms) 45 .…”

“…Histologically, PMH does not appear to be associated with any significant abnormalities of the dermis apart from a decrease in epidermal pigment, but a mild perifollicular infiltrate of lymphocytes has been observed in some, but by no means all, lesional skin samples. 2,4,[6][7][8][9][10] Detailed ultrastructural studies have provided evidence that PMH results from altered melanogenesis, leading to reduced pigmentation, and changes in melanosome size, aggregation, maturation and distribution. 2,3,6,[8][9][11][12] Furthermore, it does not appear that defects in melanosome degradation play a role in the pathophysiology of PMH as there is no evidence for disintegrated melanosomes in the lysosomal compartments of PMH lesions.…”

“…2,4,[6][7][8][9][10] Detailed ultrastructural studies have provided evidence that PMH results from altered melanogenesis, leading to reduced pigmentation, and changes in melanosome size, aggregation, maturation and distribution. 2,3,6,[8][9][11][12] Furthermore, it does not appear that defects in melanosome degradation play a role in the pathophysiology of PMH as there is no evidence for disintegrated melanosomes in the lysosomal compartments of PMH lesions. 12 Evidence supporting a potential role for Cutibacterium acnes in the aetiology of PMH While the underlying cause of PMH is still not clear, a pathogenic role for the Gram-positive, anaerobic bacterium C. acnes in the aetiology of the condition has been proposed, possibly via the production of a depigmenting factor or an agent that interferes with melanogenesis.…”

“…Treatments for PMH based on topical corticosteroids and topical or systemic antifungals have not proved efficacious, but repigmentation of the skin can be achieved using ultraviolet light A (UVA) or narrow-band UVB (NB-UVB)-based treatments, either as a monotherapy or in combination with topical or oral antimicrobials. 1,6,9,10,[19][20][21][22][23][24] Such UV treatments are believed to work by stimulating melanogenesis and, potentially, inhibition of C. acnes in the case of NB-UVB (see Section "Antibacterial therapy versus phototherapy"), but the results appear variable and in many cases are only temporary leading to recurrence of the condition. 6,20,21,24 In a within-patient, left-right trunk comparison study, Relyeld et al 25 demonstrated that topical treatment with 5% benzoyl peroxide (BPO) (morning) and 1% clindamycin hydrogel (night-time) in combination with UVA radiation (antibacterial therapy arm) was much superior for repigmentation versus 0.05% fluticasone propionate and UVA treatment only (anti-inflammatory therapy arm).…”

“…1,3 PMH is found worldwide and affects different Fitzpatrick skin types as well as both sexes, but the disorder does appear to be much more prevalent in females. 1,[4][5][6][7] PMH is often misdiagnosed as the fungal infection pityriasis versicolor, pityriasis alba or postinflammatory hypopigmentation, and can remain stable, progress slowly over a long time period or, in some cases, spontaneously disappear after mid-life. 1,3,4,8 While the exact incidence of PMH within different populations is unclear, it is likely to be an under-reported disorder as some cases may be misdiagnosed and not all patients, particularly males, will see a clinician for treatment.…”