THE PHENOMENON OF HALO‐LIKE DISAPPEARANCE OF THE MONGOLIAN SPOT ON LESIONS COMBINED WITH CAFÉ AU LAIT SPOT OR ACQUIRED PIGMENTED NEVUS

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Abstract
When café au lait spots or pigmented nevi were combined with Mongolian spot lesions, whitish haloes were observed in the areas surrounding these café au lait spots and pigmented nevi. The pathogenesis of this halo‐like phenomenon was investigated. The materials were two Japanese girls who had Mongolian spots present at birth over the sacrum and buttocks. In case 1, an eight‐month‐old, café au lait spots and in case 2, a six‐month‐old, brownish black pigmented spots appeared about one month after birth and gradually increased in size and number on the trunk and extremities. In the café au lait spot and pigmented nevus (histologically compound type) lesions and their boundary areas, a whitish halo‐like zone, dermal melanocytes were small and round, as compared with those of surrounding Mongolian spots, although only slightly decreased in number. The characteristic bipolar dendrites were almost imperceptible. The dopa reaction of dermal melanocytes was also decreased. In the boundary halo‐like areas in both cases, epidermal melanin granules and dopa‐positive melanocytes were almost identical to those of the surrounding Mongolian spot.Mongolian spots were already present at birth in both cases, but the café au lait spots and pigmented nevi definitely appeared to arise on these Mongolian spot after birth. The Mongolian spots seemed to disappear at the sites of café au lait spots, pigmented nevi and boundary areas, perhaps a kind of Sutton's phenomenon.