​Dermatology - Hypersensitivity Vasculitis

​Dermatology - Hypersensitivity vasculitis
Hypersensitivity vasculitis refers to a diverse collection of vasculitides that are linked to an exaggerated immune response to antigens derived from infectious organisms, medications, or other external or internal causes. Prior to the commencement, a recently introduced medication is a probable cause, along with the possibility of an infection, a recognized vascular/connective tissue disorder, or paraproteinemia.
The onset and duration can be categorized as acute (occurring within days, such as in cases of drug-induced or idiopathic causes), subacute (lasting for weeks, particularly in urticarial kinds), or chronic (recurring over a period of years).

Systemic vascular involvement mostly affects the kidney, muscles, joints, GI tract, and peripheral nerves. Common symptoms of this condition include itching and a sensation of burning pain. However, it is possible for individuals to have no symptoms at all. In some cases, there may also be other symptoms such as fever, general discomfort, signs of nerve damage in the limbs, abdominal pain due to reduced blood flow to the intestines, joint pain, muscle pain, presence of blood in urine, and involvement of the central nervous system.
Abnormalities
The defining characteristic is palpable purpura, which refers to visible petechiae that appear as bright red, well-defined macules and papules with a central, dot-like bleeding. This is in contrast to petechiae caused by coagulation abnormalities or thrombocytopenia, which are flat and hence not able to be felt. The lesions are distributed sporadically, either separate or merging together, and are mainly confined to the lower extremities and ankles but can extend to the buttocks and arms. Stasis exacerbates or triggers lesions. The lesions do not lose their color, remaining red, and may even darken to purple or black. During severe inflammation, purpuric papules transform into hemorrhagic blisters, undergo necrosis, and may even develop ulcers.

The diagnosis relies on the observation of clinical features and the examination of tissue samples under a microscope. The possible causes of the condition include thrombocytopenic purpura, exanthematous drug eruption accompanied by thrombocytopenia, disseminated intravascular coagulation with purpura fulminans, septic vasculitis (such as rickettsial spotted fevers), septic emboli (related to infective endocarditis), bacteremia (including disseminated gonococcal infection and acute/chronic meningococcemia), pigmented purpura, and other noninfectious vasculitides.


Administer antibiotics to patients who develop vasculitis subsequent to a bacterial infection. Administer prednisone to patients with moderate-to-severe disease, along with cytotoxic immunosuppressants such as cyclophosphamide or azathioprine, or cyclosporine and intravenous immunoglobulin for severe disease.