Comment
Our case highlights a distinct clinical presentation of hydralazine-induced ANCA-positive cutaneous vasculitis associated with severe involvement of the aerodigestive tract with gastrointestinal tract bleeding and airway compromise requiring intubation. Although discontinuation of hydralazine and in certain cases the addition of immunosuppressive agents may be adequate for resolution of symptoms, some cases progress despite treatment, leading to skin grafting, amputation, and death.3,4 Therefore, early recognition of hydralazine-induced cutaneous vasculitis and discontinuation of hydralazine are of paramount importance.
Reporting hydralazine-induced vasculitis is valuable because of its unique cutaneous, extracutaneous, and serologic findings. In our case, the cutaneous vasculitis presented clinically with acral hemorrhagic vesiculopustules and necrotic ulcerations resembling septic emboli, as opposed to classic lesions of palpable purpura typical of drug-induced leukocytoclastic vasculitis. Similar cutaneous findings have been described in other cases of hydralazine-induced vasculitis, indicating that this pattern of acral pseudoembolic vesiculopustules with necrosis and ulceration is characteristic of this entity.1,3,6 In addition, involvement of the oral cavity, larynx, and gastrointestinal tract have been reported in cases of hydralazine-induced vasculitis, indicating mucosal involvement is an important feature of this disease.3,6 Although involvement of the oral mucosa, larynx, and acral sites appears to be characteristic, the exact basis for this site localization remains elusive. A precedent has been established for a similar pattern of intraoral and laryngeal involvement in other ANCA-positive vasculitic syndromes, most notably Wegener granulomatosis.7 Similarly, there are certain occlusive vasculitic syndromes that show acral localization including chronic septic vasculitis and vasculitis of collagen vascular disease.
Serologic trends can aid in diagnosing hydralazine-induced vasculitis. In theory, the nonspecific cutaneous findings, often in association with joint pain and positive antinuclear antibodies, may lead clinicians to the misdiagnosis of a connective tissue disease, such as systemic lupus erythematosus (SLE). However, unlike SLE, hydralazine-induced vasculitis is associated with positive ANCAs, while antibodies against double-stranded DNA, a highly specific antibody for SLE, are uncommon.8,9 Our patient had both positive perinuclear ANCA with cytoplasmic ANCA as well as a positive antihistone antibodies, a combination highly suggestive of a drug-induced process.
Despite the often acute presentation of hydralazine-induced ANCA-positive vasculitis, afflicted patients have characteristically been on the drug for a long period of time. Our patient is exemplary of most reported cases, as the time from initiation of hydralazine to onset of vasculitis was 2 years.4
The mechanism by which hydralazine causes this reaction is still a matter of debate. It seems clear that there are certain at-risk populations, such as slow acetylators and patients with an underlying hypercoagulable state. There are several theories by which hydralazine induces autoantibody formation. The first involves hydralazine metabolization by MPO released from activated neutrophils to form reactive intermediate metabolites. Such metabolites can be cytotoxic and may cause abnormal degradation of chromatin in susceptible individuals, leading to an autoimmune response against histone-DNA complexes. Alternatively, hydralazine may act as a hapten and bind to MPO, inducing an immune response against the hydralazine-MPO complex, with resultant formation of anti-MPO antibodies in susceptible individuals.10
Conclusion
Hydralazine-induced ANCA-positive vasculitis is a syndromic complex characterized by a distinctive clinical presentation comprising acral hemorrhagic vesiculopustules and necrotic ulcerations, at times with severe mucosal involvement along with a characteristic ANCA-positive serologic profile. Drug withdrawal is the cornerstone of therapy, and depending on the severity of symptoms, additional immunosuppressive treatment such as corticosteroids may be necessary. Older age of onset, female gender, and underlying autoimmune diatheses likely define important risk factors. With more recognition and reporting of this disease, further trends in both clinical and serological presentation will emerge.