Hypocomplementaemic urticarial vasculitis syndrome: a mimicker of systemic lupus erythematosus

Urticarial vasculitis

Urticarial vasculitis is a rare clinicopathologic entity that is characterized by chronic or recurrent episodes of urticarial lesions. Skin findings of this disease can be difficult to distinguish visually from those of chronic idiopathic urticaria but are unique in that individual lesions persist for ≥24 hours and can leave behind dusky hyperpigmentation. This disease is most often idiopathic but has been linked to certain drugs, infections, autoimmune connective disease, myelodysplastic disorders, and malignancies. More recently, some authors have reported associations between urticarial vasculitis and COVID-19, as well as influenza A/H1N1 infection. Urticarial vasculitis can extend systemically as well, most often affecting the musculoskeletal, renal, pulmonary, gastrointestinal, and ocular systems. Features of leukocytoclastic vasculitis seen on histopathologic examination are diagnostic of this disease, but not always seen. In practice, antibiotics, dapsone, colchicine, and hydroxychloroquine are popular first-line therapies, especially for mild cutaneous disease. In more severe cases, immunosuppressives, including methotrexate, mycophenolate mofetil, azathioprine, and cyclosporine, as well as corticosteroids, may be necessary for control. More recently, select biologic therapies, including rituximab, omalizumab, and interleukin-1 inhibitors have shown promise for the treatment of recalcitrant or refractory cases.

A case of urticarial vasculitis in a female patient with lupus: Mycoplasma pneumoniae infection or lupus reactivation?

A 17-year-old female patient affected by systemic lupus erythematosus (SLE) (who had been taking 300 mg/die of hydroxychloroquine for 3 years), Graves' disease (treated with 10 mg/die of tapazole), and celiac disease came to our attention for urticarial vasculitis. She had been taking prednisone (25 mg/die) for 3 days, and her blood tests showed high levels of Mycoplasma pneumoniae IgM and IgG antibodies. The association between urticaria and M. pneumoniae infections can be present in up to 7% of the cases and, to the best of our knowledge, only two reports of urticarial vasculitis and M. pneumoniae in adults are available in the literature. Urticarial vasculitis can also be a rare cutaneous manifestation of SLE (affecting 2% of the patients), and our case is the first in the literature describing the coexistence of M. pneumoniae infection, SLE, and urticarial vasculitis in a pediatric patient, a case that rises an important differential diagnosis issue about the origin of urticarial vasculitis: SLE reactivation or urticarial vasculitis due to M. pneumoniae infection?