Esson GA, Hussain AB, Meggitt SJ, et al. - Cutaneous signs can often provide diagnostic hints of underlying systemic diseases causing acute kidney injury (AKI), therefore, in this review, cutaneous findings of diseases causing AKI in adults are summarized. Understanding such cutaneous signs may allow earlier diagnosis of underlying kidney disease as well as facilitate management approaches in a timely manner.

• Diseases causing AKI with cutaneous manifestations include: acute interstitial nephritis (AIN), polyarteritis nodosa (PAN), Kawasaki's disease, granulomatosis with polyangiitis (GPA) (previously Wegener's granulomatosis), microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis (previously Churg-Strauss syndrome).

• In addition, Henoch-Schonlein purpura, cryoglobulinemia, Sjogren's Syndrome, systemic sclerosis, nephrogenic systemic fibrosis, dermatomyositis, systemic lupus erythematosus, amyloidosis, and cholesterol embolization syndrome were also highlighted under this group.

• In AIN, rash is thought to be present in around 20-30% of cases, rash is typically a non-specific maculopapular or morbilliform exanthem, initiating on the trunk prior to spreading to the limbs and neck, and lesions tend to blanch with pressure but could be purpuric on the lower limbs.

• In PAN, cutaneous lesions occur mainly on legs and feet and include palpable purpura, tender subcutaneous nodules, livedo reticularis, and digital ischemia.

• In Kawasaki’s Disease, morbilliform rash, erythema, edema of acral / palmar sites with subsequent desquamation, oral (cheilitis) and eye mucosal involvement were reported.

• In GPA, findings were similar to those in PAN, and blistering and ulceration can occur, pyoderma gangrenosum-like lesions, and oral disease – ulceration, gingivitis were noted.

• In cholesterol embolization syndrome, the most common findings include livedo reticularis (49%), digital gangrene (35%), cyanosis (28%), ulceration (17%), nodules (10%), and purpura (9%).

• After a Spanish study of 375 COVID-19 cases, cutaneous lesions were defined into five subtypes: maculopapular eruptions occurring most often (47%), acral erythema with vesicles or pustules (pseudo-chilblains) (19%), urticarial lesions (19%), vesicular eruptions (9%) and livedo or necrosis (6%).