Non-Caseating Granulomas, and What the Culture Might Still Say
A biopsy showing non-caseating granulomas fits sarcoidosis well — but sarcoidosis is a diagnosis of exclusion, and the specific thing being excluded, an indolent mycobacterial or fungal infection, takes weeks to rule out by culture, weeks a genuinely breathless patient may not want to wait.
Beatriz F., a 34-year-old immigration attorney, presented with six weeks of progressive dyspnea on exertion, dry cough, and low-grade fevers, prompting a CT chest that showed mediastinal and bilateral hilar lymphadenopathy along with scattered small pulmonary nodules. Endobronchial ultrasound-guided biopsy of a subcarinal node returned non-caseating granulomatous inflammation — a finding consistent with sarcoidosis, and the one her pulmonology team had suspected clinically from the imaging pattern alone. AFB and fungal smears from the same tissue were negative, though cultures for both, which take considerably longer to result, remain pending.
That pending-culture detail is the entire reason today's consult exists rather than a straightforward decision to treat. Sarcoidosis, per current ATS/ERS/WASOG guidance, is formally a diagnosis of exclusion — non-caseating granulomas look essentially identical on histology whether they arise from sarcoidosis or from an indolent granulomatous infection, most feared among them tuberculosis, which a negative AFB smear meaningfully lowers the probability of but does not eliminate, since smear sensitivity for paucibacillary disease is genuinely limited. The clinical stakes of getting this wrong run in one direction specifically: corticosteroids given to a patient harboring unrecognized active tuberculosis or an endemic fungal infection risk genuine dissemination, a severe and well-documented complication precisely because steroids suppress the granulomatous response that had been containing the organism. Beatriz otherwise has no significant past medical history, takes no regular medications, and describes herself, until six weeks ago, as someone who “never gets sick” — a fact her partner echoed independently when asked. She has no reported TB contacts, was raised and has lived entirely in the same non-endemic region, has never traveled outside the country, and has no history of significant immunosuppression — a reassuring baseline, though one that hadn't yet been formally quantified against a real epidemiologic risk framework before today, and one that stands in real tension with just how breathless and fatigued she has become in a relatively short window for a disease as typically indolent as sarcoidosis usually is.
Pulmonology consult, biopsy result in hand, cultures still pending
I'd hold corticosteroids until AFB and fungal cultures result. This is exactly the scenario the diagnosis-of-exclusion framing exists for — non-caseating granulomas look the same whether they come from sarcoidosis or an indolent mycobacterial or fungal infection, and if we're wrong and treat with steroids first, we risk genuine dissemination. That's not a theoretical caution — it's a well-documented, severe complication precisely because steroids suppress the granulomatous containment that's been holding an occult infection in check.
I don't dispute the risk if she's actually infected — my concern is the real cost of assuming she is for six weeks while cultures incubate. She's progressively more short of breath, and untreated symptomatic sarcoidosis during that window isn't free either.
I take the dissemination risk seriously, genuinely — but her negative smears and clean exposure history make active TB or an endemic fungal process fairly unlikely here, and I don't think 'possible' should function the same as 'likely enough to justify weeks of untreated dyspnea.'
I want to push on something in both of your framings: neither of you has actually quantified her pretest probability yet — you're each reasoning from 'negative smear, low risk' and 'real risk, be cautious' without the specific epidemiologic history that would tell us how low is actually low for her.
A formal TB risk assessment — documented contact history, country-of-origin/travel review, prior testing — plus an interferon-gamma release assay, done now rather than waited on passively, gives us a real number to reason from instead of a general impression. If that comes back reassuring alongside her already-negative smears, I'd support starting a modest corticosteroid course for symptom control while cultures continue, rather than either full commitment to wait six weeks or full commitment to treat today.
Agreed: formal TB risk assessment and IGRA sent today, NSAIDs for interim symptom control, and corticosteroids held pending that result — explicitly not pending the full culture turnaround, since the clinical pharmacologist's risk-quantification step gave the team a faster, real answer to act on.
Her IGRA returned negative three days later, and corticosteroids were started that same day given her reassuring composite risk picture — with a plan to reassess immediately, and stop steroids, if the pending cultures return positive for any mycobacterial or fungal organism.