Black Maculae between the Toes: A Rare Form of Laugier-Hunziker Syndrome?

Sir,

A 65-year-old man presented with irregular black maculae between all 10 toes with no progress for 30 months [Figure 1]. He had white maceration between some toes due to hyperhidrosis of feet over the past decades. He had been given intermittent itraconazole in a local hospital at a dosage of 400 mg daily for 1 week every month for 3 months to treat toenail onychomycosis, which was subsequently cured; however, the black maculae between the toes had no change. We gave this patient mycological microscopy and culture of samples taken from black maculae between the toes several times but the results were negative. Dermoscopy on the dark spot between the third and fourth toes of the left foot exhibited unsymmetrical pigmentation without blue-white veil, which did not show a typical character of melanoma [Figure 2a]. After a detailed examination of the skin, we found black spots on the lip and oral mucosa [Figure 2b] with unknowing disease course, but no abnormity on fingernail, toenails, or genitalia was seen. Biopsy was conducted on the dark spot between the third and fourth toes of the left foot and histopathology showed epidermal acanthosis and trochanterellus extension [Figure 2c], and periodic acid-Schiff (PAS) staining was negative. Immunohistochemistry staining of Sox10 [Figure 2d] and HMB45 [Figure 2e] antibodies both presented some positive melanocytes in trochanterellus. The patient underwent enteroscopy examination which exhibited that colorectum mucosa had no obvious abnormity [Figure 2f]. Based on the clinical manifestation and the results of the accessory examinations, we diagnosed this case as Laugier–Hunziker syndrome (LHS), which to our knowledge was the first case report of LHS presenting melanotic macules between all the toes. There was no family history of similar complaints. This elderly patient did not care deeply about these “unbeautiful” melanotic macules and refused to accept our treatment suggestions including any topical and systemic management.

Figure 1

Irregular black maculae between all 10 toes, and white maceration was seen between some toes

Figure 2

(a) Unsymmetrical pigmentation without blue-white veil under dermoscopy, (b) labial and oral melanotic macules, (c) histopathology showed epidermal acanthosis and trochanterellus extension, (d and e) Sox10 and HMB45 staining both exhibited positive melanocytes in trochanterellus (×200), (f) colorectum mucosa without obvious abnormity

Black maculae between the toes are not a very common symptom, and the most probable diagnosis might be black ringworm or melanoma. This patient had a long history of feet hyperhidrosis, which would increase the water content of epidermal horny layer and induce the occurrence of maceration between the toes where dermatomycosis is commonly secondary to maceration. However, consideration of black ringworm was excluded due to a negative response to broad-spectrum systemic antifungal therapy, and negative mycological microscopy and culture results and PAS staining. Melanoma merely involving the skin between all the 10 toes seems to be unlikely. A small number of epidermal melanocytes with positive staining of HMB-45 antibody are not ample evidence for diagnosing melanoma; sometimes, normal melanocytes can also present positive results with HMB-45 staining. The diagnosis of melanoma was not supported by the evidence of dermoscopy manifestation, histopathology, and immunohistochemical staining. Concerning the possibility of progression to melanoma, we think the prognosis was good because of black maculae on nonrubbing parts and long-term “inactive” clinical manifestation.

Labial and oral melanotic macules are commonly encountered in many diseases, such as LHS and Peutz–Jeghers syndrome (PJS). LHS is an acquired benign condition commonly associated with longitudinal melanonychia.[1] Gerbig and Hunziker[2] first suggested “idiopathic lenticular mucocutaneous pigmentation” in 1996 to deal with LHS with atypical features; however, more literature regarded LHS and “idiopathic lenticular mucocutaneous pigmentation” as the same notion.[34] PJS is characterized by mucocutaneous pigmentation and multiple gastrointestinal hamartomatous polyps that belong to autosomal dominant inherited disease due to LKB1/STK11 gene mutation or some other genetic disorders.[5] However in our case, the examination result of enteroscopy did not support PJS. Taking all factors into consideration, we think this patient presented a rare form of LHS: melanotic macules on lip, oral mucosa, and the skin between the toes without manifestation of longitudinal melanonychia. While encountering the black maculae between the toes, the clinicians should examine the labial and oral mucosa of the patient for the possibility of LHS.

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Conflicts of interest

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