Reflectance confocal microscopy of multiple idiopathic eruptive macular pigmentation: A case report

Idiopathic eruptive macular pigmentation (IEMP) is a rare condition which was described in 1978 by French doctors Degos et al. ¹ The first reference in the English literature was in 1996; Sanz de Galdeano et al. ² summarized the diagnostic criteria after collecting and observing five cases: (1) eruption of brownish, nonconfluent, asymptomatic macules involving the trunk, neck, and proximal extremities in children or adolescents; (2) absence of preceding inflammatory lesions; (3) no prior drug exposure; (4) basal cell layer hyperpigmentation of the epidermis and prominent dermal melanophages without visible basal layer damage or lichenoid inflammatory infiltrate; and (5) normal mast cell count.

The pathogenesis of IEMP remains unclear. It seems that sunlight is not important, as most lesions occur in photoprotected areas. ³ And there have been no reported cases of IEMP with a family history. ⁴ Hormonal factors may be involved in increased pigment production, as most patients are children or young adults. ⁵ Other related factors like inflammatory stimuli, autoimmune phenomenon have been hypothesized. ⁶ , ⁷ , ⁸ IEMP was considered to be self‐limited in months to years, ⁴ , ⁹ although one case was reported to persist for 21 years. ⁸

Currently this rare disease has not been characterized with reflectance confocal microscopy (RCM), which has proven to be an important noninvasive diagnostic tool, especially to characterizing melanocytic‐related skin lesions. ¹⁰ We report a case of multiple IEMP of a teenage girl, with a description of RCM images, and compared RCM images with histopathology.

A 12‐year‐old girl presented discrete class elliptic brown macules and patches on the neck, trunk, upper arms, and upper legs of more than 2 years’ duration, without any clinical symptoms, there was no previous history of an inflammatory process, erythema, scaling. The patient has no other underlying disease. She had no history of any specific food or drug medication, no history of exposure to radioactive or other toxic substances. Treatments for the skin condition prescribed by outside dermatologists included black light (PUVA) treatment, oral vitamin C and vitamin E, and external use hydroquinone cream. The local patches were slightly lightened, but not noticeable. Physical examination showed multiple, discrete, round to oval, brown macules and patches with a smooth surface were seen on the neck, trunk, upper arms, and upper legs; adjacent lesions have a tendency of fusion (Figure 1). Hair, nails, and mucosae were normal. Lesions failed to elicit Darier sign.

FIGURE 1.

Multiple, brown, non‐scaly macules and patches. (A) Abdomen, (B) waist, (C) upper arm, (D) upper legs

Routine examination of the blood, urine, and stool and blood biochemistry were all in the normal range. RCM imaging revealed cuticle layer is normal, and the dermal papillary rings are intact. Compared with normal skin, the bright dermal papillary rings varying in size and shape were detected in the basal layer; hyper‐reflective melanophages can be seen in each of the dermal papillary rings. There are no melanocytes in the deep dermis below the dermal papillary layer (Figure 2). Histopathologic examination revealed the cuticle and spinous layers are normal, increased pigmentation in the basal‐cell layer, and scattered melanophages in the papillary dermis without visible basal‐cell layer damage or lichenoid inflammatory infiltrate and normal mast cell count. No abnormal pigment distribution was observed in the deeper dermis (Figure 3). ¹¹

FIGURE 2.

The reflectance confocal microscopy (RCM) images of the cuticle layer (A), basal layer (B), and dermis (E) of abdominal lesions, the cuticle (C) and basal layer (D) of lesions on the waist, the basal layer of the normal skin on the lower leg (F). The RCM images showed the cuticle layer of lesions is normal (A and C). Compared to the basal layer of normal skin in the lower leg (F), the dermal papillary rings are intact but with larger diameter, bright dermal papillary rings varying in size and shape were detected in the basal layer, hyper‐reflective melanophages can be seen in each of the dermal papillary rings (B and D). Melanocytes are not visible in the dermis below the superficial dermis (E). There was no obvious damage in basal layer or lichenoid inflammatory infiltrate of the three sites

FIGURE 3.

Histopathologic examination revealed the cuticle and spinous layers are normal, increased pigmentation of the basal‐cell layer, and scattered melanophages in each of the papillary dermis. No abnormal pigment distribution was observed in the dermis below the dermal papillary layer. No visible basal layer damage or lichenoid inflammatory infiltrate and normal mast cell counts. (Hematoxylin–eosin stain 4x original magnification)

All the findings in RCM images could be confirmed by histological examination. As far as we know, this is the first description of RCM features of IEMP. The description of this case is aimed to provide a better understanding of this rare disease. It is a supplement to the diagnostic criteria of such clinical pigmentation disease.