Fever and Rash in Immunocompromised Patients

Knowing the immune status of your patient is crucial since the differential diagnosis is expanded considerably in immunocompromised patients, and the suspicion for infectious causes is much higher (although these patients are often on multiple medications that can cause rashes).

As a general rule, for any new skin lesion in an immuncompromised patient, you should have a very low threshold to obtain a skin biopsy to rule out infection.

A full differential diagnosis is impossible to list here but all types of infection must be considered: bacterial, fungal, viral, and even parasitic. Here are a few common etiologies to consider in the immunocompromised patient population in addition to the usual suspects like Staph and Strep infections.

Pseudomonas – one of the most feared pathogens in immunocompromised (particularly neutropenic) patients, and 1/3rd of patients with systemic Pseudomonas infection have cutaneous manifestations which can include folliculitis, abscesses, cellulitis, vesicle, nodules, plaques, petechiae, etc. The classic lesion is Echthyma Gangrenosum which is an ulcerated lesion with a necrotic center after starting off as a painful erythematous macular lesion. Of note, other bugs (bacterial and fungal) can cause this as well. Other bacteria which can cause lesions including Echthyma gangrenosum include Stenotrophomonas (gram negative bacillus that causes nosocomial infections in the ICU), Aeromonas, Enterobacter, Strep, and Clostridium species.

Candida - ~15% of patients with disseminated candidiasis present with skin lesions, which again can be variable but often present as skin nodules.

Molds – Aspergillus, Fusarium, Mucor – all can cause skin lesions with disseminated disease, including Echthyma gangrenosum.

Cryptococcus – commonly causes skin lesions in 10-20% of disseminated cases.

Endemic Fungi - disseminated cocci, histoplasmosis, blastomycosis

Nocardia - infection usually starts in the lungs and disseminates, commonly causing a variety of skin lesions including abscesses, pustules, and nodules.

TB – can have a variety of skin manifestations, as can non-tuberculous mycobacteria.

Viruses – many different viruses can cause fever and rash in immunocompromised patients, but be especially wary for HSV and VZV, especially when vesicular lesions are present.

(Chanu Rhee MD, 6/3/11)