Dermatitis cruris pustulosa et atrophicans

A 38-year-old female presented with multiple, recurrent, asymptomatic pus-filled lesions, and hair loss over both legs for 2 years. There was no history of similar lesions elsewhere. She also had a history of regular coconut oil application over bilateral legs and forearms for the past 10 years. On examination, multiple pustules were present over the bilateral leg’s anterior and lateral aspects in a symmetric distribution. Multiple areas of rings of exfoliation surrounding the pustules with intervening areas of atrophy and scarring alopecia were seen [Figure 1]. On histological examination, there was acanthosis and perifollicular neutrophilic and lymphocytic infiltrates [Figure 2]. Based on clinical and histopathological examination, dermatitis cruris pustulosa et atrophicans was diagnosed.

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Figure 1:

Multiple follicular-based pustules symmetrically involving the bilateral anterior aspect of both legs with intervening areas of atrophy and scarring alopecia.

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Figure 2:

Predominantly neutrophilic infiltrates surrounding the hair follicle were noted (Hematoxylin and Eosin stain, ×100 magnification).

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The lesions significantly improved with oral minocycline 100 mg daily for 3 months.

Dermatitis cruris pustulosa et atrophicans is a chronic superficial folliculitis whose etiology is unknown. Staphylococcus aureus is thought to be one of the prime causative agents. It is usually symmetrical, involving bilateral legs. Rarely, other sites such as the upper limb, beard, and axilla can also be involved. The triggering factors are climate, occlusion, and clothing. In histological examination, there can be hyperkeratosis, acanthosis, and perifollicular infiltrates composed of neutrophils, lymphocytes, and rarely plasma cells. It causes significant scarring alopecia, and it is generally resistant to therapy. The treatment options are dapsone, minocycline, rifampicin, ciprofloxacin, and cotrimoxazole.^[1]