Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

Opportunistic Infections in Immunocompromised Patients

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In one line

·HIV (CD4-driven), transplant (time-based), neutropenic (low white cells), complement (body defense), B-cell.

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Normal physiology

·Layered immunity prevents OIs. Keep that picture in your head, because the weird findings only make sense as a change from it. When this normal job fails, weak immunity by type shows certain infection patterns — that is the upstream break we are about to trace.

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What goes wrong

·Usually one broken thing explains all the weird findings together.

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Hallmark signs

·Fever that won't go away or keeps coming back
·Pneumonia with cough, shortness of breath, and low oxygen
·White patches or sores in the mouth or throat (thrush)
·Diarrhea that lasts for weeks
·Blurry vision or floating spots in one or both eyes
·Painful blisters or rash on the skin, often in a strip along one side of the body
·Severe headache, stiff neck, confusion, or seizures
·Night sweats that drench clothes and sheets

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Red flags · escalate now

·New or worsening confusion, seizures, or severe headache—may signal brain infection (meningitis or encephalitis)
·Shortness of breath with low oxygen levels—may be life-threatening pneumonia from Pneumocystis, CMV, or fungi
·Sudden vision loss or blurry vision—may be CMV retinitis that can cause permanent blindness if not treated fast
·High fever with very low blood pressure or fast heart rate—may be sepsis (infection in the bloodstream spreading everywhere)
·Severe abdominal pain or blood in the stool—may be invasive gut infection or perforation (a hole in the intestine)

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Workup

·CD4 count
·HIV viral load (if HIV is the cause)
·Chest X-ray or chest CT
·Serum cryptococcal antigen (CrAg)
·Toxoplasma IgG antibody
·CMV PCR (blood) or fundoscopic eye exam
·Coughed-up mucus (Sputum) or bronchoalveolar lavage (BAL) with special stains
·Blood cultures for bacteria, fungi, and mycobacteria

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Treatment

·Start or optimize antiretroviral therapy (ART) immediately
·Give TMP-SMX (trimethoprim-sulfamethoxazole) prevention (prophylaxis) when CD4 <200
·Give azithromycin (or clarithromycin) prevention (prophylaxis) when CD4 <50
·Start valganciclovir (oral) or ganciclovir (IV) for active CMV disease
·Give amphotericin B (induction) then fluconazole (consolidation and maintenance) for cryptococcal meningitis
·Reduce or temporarily hold immunosuppressive drugs (if transplant, autoimmune disease, or cancer patient) when safe
·Give high-dose TMP-SMX plus prednisone for moderate-to-severe PJP (PaO₂ <70 mmHg or A-a gradient ≥35)

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NCLEX trap

·In a patient with CD4 below 200, a dry cough that has lasted 2 weeks plus a chest X-ray that looks like ground glass (hazy, not solid patches) is PJP (a fungal infection caused by Pneumocystis jirovecii) until proven otherwise. Regular antibiotics like amoxicillin kill bacteria, but PJP is a fungus — they do nothing. You need TMP-SMX (trimethoprim-sulfamethoxazole, also called Bactrim), which kills the Pneumocystis fungus. Always check the CD4 count and the X-ray pattern before choosing your drug.
·In a patient with CD4 below 100 and a new headache, you must think of cryptococcal meningitis (a fungus that gets into the fluid around the brain) or toxoplasma encephalitis (a parasite that makes brain abscesses). Both can kill if you miss them. Do a lumbar puncture (spinal tap) to check the spinal fluid for crypto antigen and look at a head CT or MRI for toxo lesions. Never assume it is just stress — the stakes are life or death.
·If you start HIV drugs (antiretrovirals, or ART) while the patient is still fighting an active opportunistic infection, the immune system wakes up too fast. It sees all the infection at once and floods the area with inflammation. This is called IRIS (immune reconstitution inflammatory syndrome), and it can make the patient sicker — fever spikes, symptoms get worse, even new problems appear. The right move: treat the OI first for 2 to 4 weeks, then start ART once the infection is under control. This gives the body time to clear the bugs without a huge inflammatory storm.
·Start PJP prevention (prophylaxis) (prevention medicine) with TMP-SMX when CD4 falls below 200, not 100. By the time CD4 hits 100, the risk of PJP is already high. Starting at 200 keeps the patient from ever getting PJP in the first place. This is the CDC and DHHS guideline: CD4 <200 = start TMP-SMX three times a week (or daily). Prevention saves lives.
·In a patient with CD4 below 100 and chronic diarrhea (lasting more than 2 weeks), think of MAC (Mycobacterium avium complex, a slow bacteria that loves the gut) or Cryptosporidium (a parasite that causes watery diarrhea). Steroids will make these infections worse by turning down the immune system even more. First, send stool cultures for parasites and acid-fast bacilli (AFB), and blood cultures for MAC. Once you know what bug it is, you can treat it — MAC needs azithromycin plus ethambutol; Cryptosporidium needs ART to rebuild the immune system (there is no great drug for crypto itself).
·Fever in an immunocompromised patient can come from three places: the opportunistic infection itself, a drug reaction (many OI drugs cause fever — TMP-SMX, rifampin, amphotericin), or a new infection on top of the OI (like a line infection or sepsis). Always do a full workup: blood cultures, repeat chest X-ray, check drug timing (did fever start after you started the med?). If you suspect drug fever, you may need to pause the drug and rechallenge it later. Never assume — think broadly and rule out each cause.

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