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- Presentation
Dermatologic Infections in the Immunocompromised Host
Description
This talk reviewed how to approach dermatologic infections in immunocompromised patients by focusing not only on rash morphology but also on the host’s immune deficit and exposure history. It covered four major immunocompromised states, with emphasis on iatrogenic immunosuppression and HIV. In patients receiving biologics, especially TNF-alpha inhibitors, the infectious risks vary by drug class and indication, with TNF blockade predisposing to granulomatous infections such as mycobacteria and fungi, as well as certain viral and bacterial infections. A Crohn’s patient on adalimumab with sporotrichoid nodules after saltwater exposure was ultimately diagnosed with Mycobacterium marinum using broad-range PCR after cultures were negative, highlighting the value of PCR and next-generation sequencing when suspicion remains high. The talk also emphasized waiting for organism identification before treating stable suspected nontuberculous mycobacterial infections when possible to avoid resistance. In HIV, the speakers stressed assessing immune status with viral load, CD4 count, and sometimes CD4 percentage in acute illness, since CD4 counts can transiently fall during severe illness. They used morphology-based diagnosis, especially umbilicated papules, to frame the differential, including cryptococcosis, histoplasmosis, molluscum contagiosum, mpox, and talaromycosis (penicilliosis). Bedside diagnostic tools such as India ink, Giemsa stain, and Tzanck smear were reviewed. Mpox severity markers and evolving treatment evidence were discussed, and molluscum in advanced HIV was often managed expectantly as ART restored immunity. Overall, the session emphasized combining morphology, immune status, exposure history, and targeted diagnostic testing to diagnose and manage skin infections in immunocompromised hosts.
View moreConclusions
- TNF-alpha inhibitors increase the risk of granulomatous, fungal, viral, and bacterial infections, so the underlying medication and indication should guide the infectious differential.
- In stable suspected nontuberculous mycobacterial infection, it is often better to wait for species identification and susceptibilities before starting therapy to avoid unnecessary resistance.
- When cultures are repeatedly negative but clinical suspicion remains high, broad-range PCR and next-generation sequencing can provide a useful diagnosis from skin tissue.
- In HIV, immune status should be interpreted with viral load, CD4 count, and sometimes CD4 percentage, because acute illness can transiently depress the absolute CD4 count.
- Umbilicated papules in patients with HIV have a focused differential that includes cryptococcosis, histoplasmosis, molluscum contagiosum, mpox, and penicilliosis/talaromycosis.
- Morphology and an exposure history are more useful than CD4 count alone for narrowing infectious skin diagnoses in immunocompromised patients.
- Disseminated cryptococcosis, histoplasmosis, and penicilliosis/talaromycosis can present with distinctive umbilicated lesions and may signal severe systemic disease.
- Molluscum contagiosum can be extensive in uncontrolled HIV, but lesions may improve with immune reconstitution on ART even without specific topical treatment.
- Severe mpox is associated with uncontrolled HIV, delayed antiviral treatment, necrotic skin findings, and potentially fatal hyperinflammatory complications.
- Overall, careful host assessment plus lesion morphology and targeted molecular diagnostics improve recognition and management of dermatologic infections in immunocompromised patients.
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