The clinical differential diagnosis for PLEVA includes disseminated herpes zoster, varicella-zoster virus or coxsackievirus infections, lymphomatoid papulosis, angiodestructive lymphoma such as extranodal natural killer/T-cell lymphoma, drug eruption, arthropod bite, erythema multiforme, ecthyma, ecthyma gangrenosum, necrotic folliculitis, and cutaneous small vessel vasculitis. To differentiate between these diagnoses and PLEVA or FUMHD, it is important to take a strong clinical history. For example, for varicella-zoster virus and coxsackievirus infections, exposure history to the viruses and vaccination history for varicella-zoster virus can help elucidate the diagnosis.
Skin biopsy can help differentiate between these entities and PLEVA or FUMHD. The histopathology of a nonulcerated lesion of FUMHD shows parakeratosis, spongiosis, and lymphocyte exocytosis, as well as lymphocytic vasculitis—findings commonly seen in PLEVA. With the ulceronecrotic lesions of FUMHD, epidermal necrosis and ulceration can be seen microscopically.2 Although skin biopsy is not absolutely necessary for making the diagnosis of PLEVA, it can be helpful.3 However, given the dramatic and extreme clinical impression with an extensive differential diagnosis that includes disorders ranging from infectious to neoplastic, biopsy of FUMHD with clinicopathologic correlation often is required.
It is important to avoid biopsying ulcerated lesions of FUMHD, as the histopathologic findings are more likely to be nonspecific. Additionally, nonspecific features often are seen with immunohistochemistry; abnormal laboratory testing may be seen in FUMHD, but there is no specific test to diagnose FUMHD.2 Finally, a predominantly CD8+ cell infiltrate was seen in 4 of 6 cases of FUMHD, with 2 cases showing a mixed infiltrate of CD8+ and CD4+ cells.5,7-10
Although no unified diagnostic criterion exists for FUMHD, Nofal et al2 proposed criteria comprised of constant features, which are found in every case of FUMHD and can confirm the diagnosis alone, and variable features to help ensure that cases of FUMHD are not missed. The constant features include fever, acute onset of generalized ulceronecrotic papules and plaques, a course that is rapid and progressive (without a tendency for spontaneous resolution), and histopathology that is consistent with PLEVA. The variable features include history of PLEVA, involvement of mucous membranes, and systemic involvement.2
No single unifying treatment modality for all cases of FUMHD has been described. Immunosuppressive drugs (eg, systemic steroids, methotrexate), antibiotics, antivirals, phototherapy, intravenous immunoglobulin, and dapsone have been tried in patients with FUMHD.2 Combination therapy with an oral medication such as erythromycin or methotrexate and psoralen plus UVA may be effective for FUMHD.3 Additionally, some authors believe that patients with FUMHD should be treated similar to burn victims with intensive supportive care.2