Asymptomatic Hyperpigmented Macules and Patches on the Trunk.

Abstract

DISCUSSION First described by Degos et al in 1978, it is a condition manifested by asymptomatic pigmented macules that can involve the neck, trunk, and proximal limbs. It is a rare condition, of which less than 50 cases have been reported in the literature. The majority of cases have been reported among the Asian population, although the disease has been reported in white, Hispanics, and African Americans. Age of onset ranges from 1 to 31 years, affecting men and women equally. Although the etiology of IEMP is unknown, hormonal factors and autoimmune disorders may play a role, as evidenced by reported exacerbation during pregnancy. Generally thought to be self-limited, there is a gradual progressive disappearance of lesions over months to years. However, a case was reported to have lasted 21 years, in which the condition followed a relapsing–remitting course. Histologic examination is characterized by increased pigmentation of the basal layer in an otherwise normal epidermis. Pigmentary incontinence or melanophages in the papillary dermis is a feature described in the majority of cases, but a few cases have been reported where there is an absence of this feature, and in the appropriate clinical setting, this did not preclude the diagnosis of IEMP. In addition, there is also a mild perivascular lymphohistiocytic infiltrate in the upper dermis with a normal mast cell count. According to Sanz de Galdeano et al, on transmission electron microscopy, the keratinocytes of the basal and suprabasal layers are filled with large numbers of mature and clustered melanosomes. The clinical differential diagnosis includes erythema dyschromicum perstans, lichen planus pigmentosus, drug eruption, and postinflammatory hyperpigmentation. Histologically, erythema dyschromicum perstans and lichen planus pigmentosus show basal cell vacuolization with necrotic keratinocytes at the dermal–epidermal junction and numerous melanophages in the papillary dermis. Our patient denied use of drugs or supplements, militating against cutaneous pigmentation produced by drugs. There were also no clinical features or history to suggest a preceding dermatosis. Dyschromatosis universalis hereditaria was considered on histologic grounds, but the clinical history of presenting in early adulthood and the absence of hypopigmented macules made this possibility unlikely. Currently, there is no standard treatment for IEMP. Fortunately, spontaneous resolution is to be expected within several months to years. NdYag laser and hydroquinone preparations have been described in the literature as possible therapy, although they have proven to be unsuccessful. In summary, diagnostic criteria for this disease, published by Sanz de Galdeano et al, include (1) eruption of brownish, nonconfluent, asymptomatic macules involving the trunk, neck, and proximal extremities in children and adolescents; (2) absence of preceding inflammatory lesions; (3) no previous 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. Besides the appearance of pigmented macules and patches, physical examination and routine laboratory tests are normal. Our case emphasizes that this condition is not exclusive to the Asian population. Additionally, although our case did reveal rare dermal melanophages, it should be noted that histologic findings may be limited to only basal hyperpigmentation without significant melanophage content.