Diagnosis: Cutaneous small-vessel leukocytoclastic vasculitis (also called hypersensitivity vasculitis).

The bilateral dependent-leg purpura with some necrotic/crusted lesions is typical. The biopsy image shows small-vessel inflammation with neutrophils, leukocytoclasia (nuclear dust), erythrocyte extravasation, and vessel-wall injury, which supports this diagnosis.

It should be evaluated for triggers or systemic involvement, including recent infection, new medications, renal involvement (urinalysis), abdominal pain, arthralgia, and neuropathy. DermNet’s diagnostic summary notes that an early purpuric papule biopsied at 24-48 hours is most informative.

This chest radiograph appears to show bilateral multifocal nodular/cavitating air-space opacities, more conspicuous in the mid and lower lungs.

In the context of the preceding leukocytoclastic vasculitis-like purpura, an important unifying diagnosis is:

Granulomatosis with polyangiitis (GPA, formerly Wegener granulomatosis) with pulmonary nodules/cavitation and cutaneous small-vessel vasculitis.

However, this cannot be diagnosed from a photographed X-ray alone. Urgent alternatives include septic pulmonary emboli, pulmonary tuberculosis, fungal infection, and cavitating metastases.

Recommended urgent work-up:

If there is breathlessness, hemoptysis, fever, low oxygen saturation, reduced urine output, or blood in urine, this needs immediate hospital assessment.