ALDY was originally described by Annessi et al.² in children and young adults (median age of 10). Because it can affect older patients,^1,3 renaming the entity to “annular lichenoid dermatosis” was proposed. ALDY lacks gender predilection. Most cases were described in individuals with Mediterranean descent, but cases from Japan, other areas in Europe, and the United States had been reported. ALDY has not been described in African Americans.

The pathogenesis of the disease is obscure. Autoimmunity, infections, and sensitization have been investigated.^1,2 Serologic studies for Lyme and parvovirus B19, and patch testing for various allergens were negative.^4,5,6 A single individual had been shown to be atopic.¹ Atopy and eczema were also noted in another case, in which ALDY occurred following hepatitis B vaccination.⁷

A T cell–mediated cytotoxic immune reaction is favored as the main underlying pathogenesis. As such, ALDY can be considered an interface dermatitis, such as lichen planus, graft-versus-host disease, or lichen sclerosus et atrophicus (LSA).

The lesions consist of persistent asymptomatic erythematous macules and annular patches with raised red-brownish border and hypopigmented center.⁸ The lesions are typically multiple, but cases with solitary lesions had been described. ALDY is usually located in the trunk, particularly on the flanks and abdomen (Fig. 48-1) and range from 3 to 10 cm in size. The axilla and neck are occasionally involved. Involvement of distal extremities, buttock, and face/scalp had not been reported. The duration of the clinical lesions prior to biopsy averages 1 to 15 months.¹ The clinical lesions can resemble morphea, MF, annular erythema, and vitiligo. A single case report described a hyperpigmented patch resembling ashy dermatosis (lichen planus pigmentosus/erythema dyschromicum perstans) adjacent to a hypopigmented lesion with erythematous border suggesting an overlapping spectrum with ALDY.⁹

The histopathology varies depending on the age of the lesion and the site of the biopsy.^1,5,11,12 Early lesions show vacuolar changes of basal keratinocytes and a band-like lymphocytic infiltrate confined at the rete tips (Fig. 48-2). There is acanthosis with prominent thinning of the rete ridges. The lichenoid process ultimately obliterates the rete tips, resulting in a characteristic quadrangular-shaped or flat-bottomed rete, associated with collections of apoptotic keratinocytes (colloid bodies) at the base of the rete ridges. Colloid bodies are typical but usually not as numerous as in lichen planus. Intraepidermal lymphocytes lack cytologic atypia. Pautrier microabscesses are absent. Admixed dermal histiocytes and superficial dermal edema might be seen.