Multiple annular plaques on the thighs of an 8-year-old girl

An 8-year-old girl, with a past personal history of idiopathic neutropenia, presented with asymptomatic lesions of the lower limbs for the previous 3 months, which appeared during winter. The patient denied any systemic symptoms. Physical examination revealed multiple erythematous to violaceous, annular, infiltrated plaques, symmetrically distributed over the buttocks and upper lateral aspects of the thighs (Fig. 1). There were no erosions or ulceration. The remainder of the examination was unremarkable. Laboratory workup, including a complete blood count, peripheral blood smear, coagulation, renal and liver functions, C-reactive protein, erythrocyte sedimentation rate, complement, and antinuclear antibodies, was normal, except for the previously known neutropenia of 600/μl, which has been stable. Histological examination of a skin biopsy demonstrated a moderately dense lymphocytic infiltrate of the superficial and deep dermis, with a predominantly perivascular and focally perieccrine distribution (Fig. 2). Cold-associated perniosis of the thighs. Since the histological findings were consistent with perniosis and given the topography of the lesions, the patient was diagnosed with cold-associated perniosis of the thighs. The lesions spontaneously evolved into subtle hyperpigmented macules, which ended up disappearing after 1 month. When questioned, the patient denied practicing horse riding or other outdoor activities on a regular basis, although she used to wear tight-fitting jeans. Cold-associated perniosis of the thighs corresponds to the entity classically known as “equestrian cold panniculitis.” It was originally described in 1980 in young, healthy women, who frequently rode horses wearing tight-fitting, uninsulated pants.1 Clinically, it presents as red-to-violaceous, indurated plaques or nodules characteristically localized on the upper lateral portions of the thighs.1 The lesions may be pruritic or painful and show central ulceration or necrosis.2, 3 Young women are, indeed, the most affected group, but in many reported cases, they did not specifically practice horse riding. Any outdoor activity, for example, hiking, cycling, or river crossing, especially if wearing tight-fitting clothes in cold weather, may originate identical lesions.2, 3 Underlying pathogenic mechanisms may encompass impaired blood circulation on the skin originating a subacute vascular and/or perivascular damage. This is different from the acute cold-induced panniculitides (Haxthausen's adiponecrosis e frigore and ice popsicle panniculitis), in which there is a primary cold-induced injury with fat necrosis.4 The main histologic feature is the presence of a superficial and deep perivascular and periadnexal lymphocytic infiltrate, similar to idiopathic perniosis. Lobular panniculitis, if present, is usually very subtle.4 Since most of the patients with cold-associated perniosis of the thighs do not practice horse riding and the histological findings are not compatible with primary panniculitis, the replacement of “equestrian cold panniculitis” with “cold-associated perniosis of the thighs” has been proposed.4 Particularly in our case, considering the morphology of the lesions, clinical differential diagnosis included chilblain lupus erythematosus, lupus tumidus, granuloma annulare, interstitial granulomatous dermatitis, or urticarial vasculitis. In fact, the clinical and histological overlap between cold-associated perniosis of the thighs and both chilblain lupus and lupus tumidus has been reported.3, 4 Despite this, the first is a benign entity, with favorable clinical course and spontaneous resolution, although potent topical corticosteroids may have a role in symptomatic treatment.2 The recognition of a classic presentation of cold-associated perniosis of the thighs, namely in young, healthy, female patients during winter, may prevent unnecessary complementary studies, which should be reserved only for atypical cases.