Light patches on the trunk may turn out to be progressive macular hypomelanosis

In his presentation titled 'Diagnoses Not to Miss,' Dr. Andrew F. Alexis provided information on tricky skin conditions such as PMH. (770 words, 3 min.

In his presentation titled “Diagnoses Not to Miss” at Skin Spectrum Summit in Montreal, Dr. Andrew F. Alexis provided information on several tricky skin conditions that can easily be mistaken for something else. Dr. Alexis said that his goal for this presentation was to broaden the presentation of dark and light spots in patients of colour.

Many of these conditions, he said, are not “everyday” conditions that dermatologists encounter in their practice. However, although often misdiagnosed, one of the more common conditions he spoke about was progressive macular hypomelanosis (PMH). 

This condition usually appears as white or light-coloured patches on the patient’s trunk. 

“Usually, when we see these little hypopigmented macules that coalesce to patches on the trunk, the diagnosis is pretty straightforward: we think tinea versicolor,” said Dr. Alexis. 

But not all of these types of patches on the trunk are tinea versicolor, he said. PMH also presents as hypopigmented macules that coalesce to patches that appear on the chest and back. 

“You often try to treat it as tinea versicolor. You give [patients] every antifungal known to man, and it just doesn’t go away,” he said.

With tinea versicolor, fine scales are often observed, but not with PMH. In cases where no scale is observed, and antifungals are ineffective, it’s often PMH, he said. 

Unlike tinea versicolor, the condition is not caused by yeast, which triggers a fungal infection. Instead, PMH is a bacterial infection, which he said is mediated by the bacteria P. acnes, also known as C. acnes. The P. acnes bacteria can be found using a Wood’s lamp, under which it fluoresces. 

According to Dr. Alexis, treatment should be directed at the P. acnes bacteria, using either a topical benzoyl peroxide wash or topical clindamycin formulations. 

Resolution should happen in approximately 12 weeks, he said. For best results, Dr. Alexis recommends phototherapy, such as narrow-band UVB, in addition to topical antimicrobial therapy. 

“With that, I hope that I have helped to broaden the differential of the common presentation of dark spots and light spots in patients of colour,” he said. 

The takeaway: PMH is a commonly misdiagnosed condition that is commonly mistaken for versicolor. Treatment should be aimed at the P.acnes bacteria, which is the cause of the condition.

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FROM THE LITERATURE ON PMH

Is Cutibacterium (previously Propionibacterium) acnes a potential pathogenic factor in the etiology of the skin disease progressive macular hypomelanosis?

Though some studies have found a link between C. acnes type III and PMH, there is still not enough conclusive evidence to determine the causal association, according to a recent study. The researchers said that the bacterium might be responsible for causing a response that leads to hypopigmentation even if no trace of the bacteria is detectable. 

From “JEADV”

Dermatoscopic features of pigmentary diseases in ethnic skin

  • A recent study evaluated the dermatoscopic features of pigmentary skin diseases, including PMH in Fitzpatrick skin types IV-VI. The researchers noted that patients with PMH show focal white areas with broken pigmentation, some white scaling, and widened skin lines under dermatoscopic examination.

    From “Indian Dermatology Online Journal”

Therapeutic response of patients with progressive macular hypomelanosis to narrowband ultraviolet B phototherapy at dermatology department, Tripoli Central Hospital, Tripoli, Libya (2008–2018)

  • A recent study found that NB-UVB phototherapy may be an effective treatment for PMH. The researchers said that in a study of 100 patients who were treated three times per week with 0.2 J/cm2— increased by 20% per session— the therapy was well-tolerated, safe, and simple to administer.

    From “ LJMS"

VIDEO: Underlying skin conditions do not increase susceptibility to Covid-19, study finds

AT THE INTERSECTION OF SKIN AND SOCIETY

  • A group of indigenous Canadians are fighting to block the appropriation of an indigenous mythical figure after the city of Vernon in British Columbia, which owns copyright over the figure, granted a children’s book author the right to use it, according to a report by The Guardian. The legendary First Nations figure, known in English as Ogopogo (known to the Syilx as n ̓x̌ax̌aitkʷ), has been compared to the Loch Ness monster. According to the report, the city of Vernon has held the copyright to the sea monster—which is said to live in Okanagan Lake—since 1956. “We equated it to someone taking ownership over the Bible and suddenly copyrighting the name Moses,” said Chief Byron Louis of the Okanagan Indian Band in an interview with The Guardian. “The idea that someone can take ownership of your teachings and your religious beliefs is absolutely unacceptable.” Read the full story here.

This Week

Something to think about during the week ahead…

Next Week

Dr. Jaggi Rao discusses signs of psoriasis and its subtypes.

Thank you to our panellists and delegates for making the Indigenous Skin Spectrum Summit a great success. Conference highlights will soon be posted to the Skin Spectrum website. As always, we welcome your questions and comments on topics in Ethnodermatology.

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