Beneath the Skin: Cutaneous Manifestations of Polyarteritis Nodosa With Suspected Renal Involvement

Polyarteritis nodosa (PAN) is a rare systemic necrotizing vasculitis that predominantly affects medium-sized muscular arteries and is typically not associated with antineutrophil cytoplasmic antibodies (ANCA).We report the case of a 40-year-old man with a history of hypertension and a three-year history of relapsing and remitting episodes of fever.It was also associated with recurrent cutaneous lesions that temporarily improved with corticosteroid therapy received from an outside physician.He reported bilateral lower-limb tingling for which he was taking oral herbal supplements.He presented with cutaneous manifestations of necrotic ulcers, hemorrhagic bullae with peripheral erythema, and purpuric plaques.He also had associated bilateral progressive lower limb edema and bilateral joint pain.Laboratory evaluation revealed a white blood cell count of 24,900/µL and a C-reactive protein level of 140 mg/L.Serum creatinine was 1.70 mg/dL, with an estimated glomerular filtration rate of 53 mL/min/1.73m² and blood urea nitrogen (BUN) of 28 mg/dL.Urine routine and microscopy showed +2 proteinuria without RBC casts or hematuria.Urinary microalbumin was 73.73 mg/L.Both p-ANCA and c-ANCA were negative, while hepatitis B surface antigen and anti-hepatitis C virus antibody testing were non-reactive.C3, C4, and IgA levels were within normal limits, and antinuclear antibody (ANA) was negative.Histopathological examination demonstrated cutaneous vasculitis characterized by a neutrophilic infiltrate with leukocytoclasia, perivascular distribution, focal endothelial swelling, fibrinoid necrosis, and thrombosis, predominantly involving medium-sized vessels.Direct immunofluorescence was negative for IgG, IgM, IgA, and C3, with no immune deposits in the vessel walls; together with negative ANCA and ANA testing, normal IgA and complement levels, and a negative infectious work-up, these findings helped narrow the differential diagnosis.The biopsy findings, in conjunction with the clinical presentation, supported a diagnosis of cutaneous PAN.The concurrent renal biochemical abnormalities raised concern for possible renal involvement; however, definitive renal vascular evaluation could not be performed.Although renal involvement attributable to PAN was not definitively established, it was clinically suspected by the nephrology and rheumatology teams.The patient received intravenous pulse cyclophosphamide (15 mg/kg once monthly for six months) in combination with systemic corticosteroid therapy consisting of an initial intravenous methylprednisolone dose followed by oral prednisolone (1 mg/kg/day) with gradual taper.Empirical antibiotics were administered along with topical wound care for the skin lesions.Following the initial treatment cycle, the white blood cell count decreased to 11,400/µL, the C-reactive protein level decreased to 9.60 mg/L, and the cutaneous lesions demonstrated marked re-epithelialization without the development of new lesions.After the completion of the treatment his renal function test (RFT) values improved and BUN was 19 mg/dL and creatinine decreased to 1.1 mg/dL.This case emphasizes that prominent cutaneous manifestations of PAN should prompt careful evaluation for systemic involvement, particularly when clinical or laboratory findings suggest possible systemic involvement.