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Pityrosporum and seborrheic keratosis: An association

  • Author(s): Borenstein, Michael;
  • Mirzabeigi, Mirjan;
  • Vincek, Vladimir
  • et al.
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Pityrosporum and seborrheic keratosis: An association
Michael Borenstein MD PhD, Mirjan Mirzabeigi MD, and Vladimir Vincek MD PhD
Dermatology Online Journal 11 (2): 3

Departments of Dermatology and Pathology, University of Miami School of Medicine, Miami, Florida, USA. vvincek@med.miami.edu

Abstract

Seborrheic keratoses (SK) are one of the most common benign tumors of the skin. Studies have suggested that human papillomavirus or a benign clonal proliferation of epidermal cells is involved in the pathogenesis of some SK's, however, this issue remains to be resolved. Pityrosporum ovale has been implicated in the pathogenesis of seborrheic dermatitis, however, its potential role in association with SK's has not been evaluated as evidenced by the fact that there are no publications in the English-language literature regarding this issue. We observed a common occurrence of Pityrosporum organisms in the stratum corneum of SK on routine histopathologic sections and decided to investigate whether there was an association between these two common entities. We found that in a majority of the SK studied Pityrosporum was present, which was significantly different from controls (verruca vulgaris and basal cell carcinoma).



Introduction

Seborrheic keratoses (SK) are common benign tumors of the skin. Studies have suggested that human papillomavirus [1] or a benign clonal proliferation of epidermal cells [2] are involved in the pathogenesis of some SK's, however, the true etiology of these lesions remains to be resolved. Pityrosporum ovale has been implicated in the pathogenesis of seborrheic dermatitis, however, its potential role in association with SK's has not been evaluated; there are no publications in the English literature regarding this issue.

Prior to starting this study, the authors observed during routine evaluations of biopsies a common occurrence of Pityrosporum organisms in the stratum corneum of SK's. Because there is no literature on this issue, the authors decided to investigate whether there was an association between these two common entities. Histopathologic sections of previously biopsied SK's were examined for the presence of Pityrosporum organisms in the stratum corneum. We found that in a majority of the SK evaluated, Pityrosporum was present, which was significantly different from controls.


Methods

One hundred consecutive case with the diagnosis of SK were pulled from the Jackson Memorial Hospital Department of Pathology files. Hematoxylin and eosin (H&E) stained sections were examined by the investigators to determine the presence of absence of Pityrosporum organisms in the stratum corneum. As a control, thirty consecutive cases of basal cell carcinoma (BCC) and 30 cases of verruca vulgaris (VV) from the trunk or face were examined. PAS staining was performed on all cases to confirm the H&E impression of the Pityrosporum presence.


Results


Figure 1 Figure 2
Figure 1. (A) H&E section of a representative SK (original magnification 40x).
Figure 2. Higher power view of the organisms in the stratum corneum (100x).

Figure 3 Figure 4
Figure 3. PAS stained section demonstrating multiple PAS positive organisms in the stratum corneum (100x).
Figure 4. Percent of cases positive for Pityrosporum organisms. There was a statistically significant difference (p<0.05) between SK and VV by Students t-test.

Figures 1-3 show an H&E section of a SK at low power (A). At higher power (B), the organisms can be seen in the stratum corneum. (C) PAS stained section at high power demonstrate multiple PAS positive organisms in the stratum corneum.

As seen in Fig. 4, Pityrosporum organisms were identified in 61 of 100 (61%) SK's on PAS stained sections. None of the thirty BCC's evaluated had evidence of spores. Pityrosporum organisms were identified in four of thirty VV (13%) evaluated. There was a statistically significant difference (p<0.05) between SK and VV by Students t-test.


Discussion

This study found that a majority of the SK's evaluated had Pityrosporum organisms in the stratum corneum. This proportion was greater than expected. Although the current study demonstrates an association between SK and Pityrosporum, it does not establish cause and effect.

There are no English language reports of an association Pityrosporum and SK in the Medline database. The only published investigation regarding this issue is in the French language literature [3]; it found no difference in the prevalence of Pityrosporum ovale in stratum corneum of SK, actinic keratosis, nevi and verruca vulgaris. The authors suggested that hyperkeratosis was the reason the Pityrosporum was present in SK.

The previous study differs from the current study in that there was no difference in the frequency of organisms in the different lesions. However, if hyperkeratosis alone were the cause of the presence of Pityrosporum (by providing a permissive environment for growth), then the VV in the current study would have been expected to have a higher percentage of positive cases. However, only 13 percent of cases of VV were positive in this study, thus suggesting that the issue may be more complex than the presence of hyperkeratosis. One possible explanation for the observed difference could be that Pityrosporum colonization is more common on the trunk and face as are seborrheic keratosis, whereas verrucae vulgaris is more common on the palms and soles. Therefore, we purposely selected cases of VV only from the trunk and face; the observed difference was still significant.

Because two common entities are compared for association, larger studies with a wider variety of controls will be needed to determine whether a true association exists. It is possible, as postulated with seborrheic dermatitis, that SK's form as the skin's response to an irritant or as a reactive phenomenon to colonization with Pityrosporum.

If this association proves to be significant and Pityrosporum is involved in the pathogenesis of SK, then it is possible that antifungal medications may be useful for the prevention or treatment of SK, as these agents are useful in seborrheic dermatitis. It would be interesting to determine if patients treated with systemic antifungal medication for onychomycosis also note disappearance or reduction of their seborrheic keratoses.

In conclusion, this study demonstrates an association between seborrheic keratoses and the presence of Pityrosporum. Further studies are needed to to clarify the relationship between these entities.

References

1. Gushi A, Kanekura T, Kanzani T, Eizuru Y. Detection and sequences of human papillomavirus DNA in nongenital seborrheic keratosis of immunopotent individuals. J Derm Science 2003 Apr; 31(2):143-9. PubMed

2. Nakkamura H, Hiroto S, Adachi S, Ozaki K, Asada H, Kitamura Y. Clonal nature of seborrheic keratosis demonstrated by using the polymorphism of the human androgen receptor locus as a marker. J Invest Derm 2001 Apr; 116(4):506-10. PubMed

3. Bourlond A, Votion V, Armijo F, Minne G. Pityrosporum ovalein keratotic lesions of seborrheic area. Ann Dermatol Venereol (French) 1984 Oct; 111(12);1081-5. PubMed

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