A painless, indurated ulcer on the penis of a truck driver has a clean base, and he has rubbery, non-tender inguinal nodes. A biopsy is taken because dark-ground microscopy is not available. Which histological pattern is most characteristic of the likely infection?

Plasma cell-rich infiltrate with obliterative endarteritis

Stellate abscesses with palisading histiocytes

Donovan bodies within large histiocytes

Caseating granulomas with Langhans giant cells

Colonoscopy in a hostel cook with bloody diarrhoea for 2 weeks shows scattered ulcers with normal mucosa between them. Biopsy: flask-shaped ulcers undermining the mucosa, with trophozoites containing ingested red cells at the ulcer edge, PAS positive. Stool culture for bacteria is negative. What is the best treatment?

Metronidazole, then a luminal agent

Endobronchial ultrasound-guided biopsy of enlarged hilar and mediastinal nodes from a schoolteacher in Pune with dry cough and erythema nodosum shows tight, non-caseating epithelioid granulomas with asteroid bodies and Schaumann bodies. ZN stain is negative. Serum ACE is raised and serum calcium is 11.2 mg/dL (normal 8.5-10.5). Her chest X-ray shows bilateral hilar lymphadenopathy with mild reticular shadows in both upper zones. She has no fever, night sweats or known contact with tuberculosis. The pulmonologist plans oral prednisolone. In this setting in India, what must be done before starting steroids?

Exclude TB with culture and CBNAAT of the tissue

Start isoniazid preventive therapy routinely

Infectious disease pathology

26 NEET-PG practice questions on Infectious disease pathology, part of Pathology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
Skin biopsy from a patient with multiple symmetrical shiny nodules, loss of the lateral eyebrows and a saddle nose: an uninvolved band of dermis just below the epidermis, and below it sheets of foamy macrophages with no well-formed granulomas. Fite-Faraco stain shows numerous bacilli in clumps. Under the Ridley-Jopling scheme, how is this classified?
1. ABorderline tuberculoid (BT)
2. BLepromatous leprosy (LL)
3. CIndeterminate leprosy
4. DTuberculoid leprosy (TT)
Show answerHide answer
Answer: B · Lepromatous leprosy (LL)
A clear subepidermal grenz zone, sheets of foamy (Virchow or lepra) cells packed with bacilli and globi, and no organised granulomas reflect poor cell-mediated (Th1) immunity: lepromatous leprosy. Tuberculoid leprosy lies at the other pole, with well-formed epithelioid granulomas that track along and destroy nerves and very few bacilli. Lepromatous patients are multibacillary and receive three-drug MDT.
- A: BT has granulomas and few bacilli, not sheets of foamy cells.
- C: Indeterminate leprosy has a sparse non-specific infiltrate around nerves and rare bacilli.
- D: TT shows epithelioid granulomas around nerves with few or no bacilli.
Remember this
A grenz zone with foamy macrophages full of bacilli means lepromatous leprosy (weak Th1); epithelioid granulomas with few bacilli mean tuberculoid.
Question 2 · Medium
A painless, indurated ulcer on the penis of a truck driver has a clean base, and he has rubbery, non-tender inguinal nodes. A biopsy is taken because dark-ground microscopy is not available. Which histological pattern is most characteristic of the likely infection?
1. AStellate abscesses with palisading histiocytes
2. BDonovan bodies within large histiocytes
3. CPlasma cell-rich infiltrate with obliterative endarteritis
4. DCaseating granulomas with Langhans giant cells
Show answerHide answer
Answer: C · Plasma cell-rich infiltrate with obliterative endarteritis
A painless indurated chancre with rubbery nodes is primary syphilis. The basic lesion in every stage is a proliferative endarteritis, with endothelial swelling and an intense perivascular infiltrate rich in plasma cells, which explains ischaemic necrosis in gummas and aortitis. Spirochaetes are shown by silver stains or anti-treponemal IHC, and serology (VDRL with TPHA) confirms the diagnosis.
- A: Stellate abscesses point to lymphogranuloma venereum or cat-scratch disease.
- B: Donovan bodies in histiocytes are diagnostic of granuloma inguinale.
- D: Caseating granulomas suggest tuberculosis.
Remember this
Syphilis histology in every stage shows obliterative endarteritis with a plasma cell-rich infiltrate.
Question 3 · Medium
Colonoscopy in a hostel cook with bloody diarrhoea for 2 weeks shows scattered ulcers with normal mucosa between them. Biopsy: flask-shaped ulcers undermining the mucosa, with trophozoites containing ingested red cells at the ulcer edge, PAS positive. Stool culture for bacteria is negative. What is the best treatment?
1. ADiloxanide furoate alone
2. BMetronidazole alone
3. CMetronidazole, then a luminal agent
4. DCiprofloxacin and steroids
Show answerHide answer
Answer: C · Metronidazole, then a luminal agent
Flask-shaped ulcers with PAS-positive trophozoites containing red cells are amoebic colitis due to Entamoeba histolytica; ingested red cells separate it from non-pathogenic E. dispar. A tissue amoebicide such as metronidazole or tinidazole kills invasive trophozoites, but cysts persist in the lumen, so a luminal agent (paromomycin or diloxanide furoate) must follow to prevent relapse and carriage. Steroids can cause fulminant amoebic colitis.
- A: A luminal agent alone does not kill invasive trophozoites.
- B: Metronidazole alone leaves luminal cysts, so relapse and spread can follow.
- D: Steroids worsen amoebic colitis and may cause perforation.
Remember this
Amoebic colitis needs metronidazole for tissue forms, then a luminal agent to clear cysts.
Question 4 · Hard
Endobronchial ultrasound-guided biopsy of enlarged hilar and mediastinal nodes from a schoolteacher in Pune with dry cough and erythema nodosum shows tight, non-caseating epithelioid granulomas with asteroid bodies and Schaumann bodies. ZN stain is negative. Serum ACE is raised and serum calcium is 11.2 mg/dL (normal 8.5-10.5). Her chest X-ray shows bilateral hilar lymphadenopathy with mild reticular shadows in both upper zones. She has no fever, night sweats or known contact with tuberculosis. The pulmonologist plans oral prednisolone. In this setting in India, what must be done before starting steroids?
1. ADo a Kveim-Siltzbach skin test
2. BExclude TB with culture and CBNAAT of the tissue
3. CStart isoniazid preventive therapy routinely
4. DRepeat serum ACE after 4 weeks
Show answerHide answer
Answer: B · Exclude TB with culture and CBNAAT of the tissue
Non-caseating granulomas with asteroid and Schaumann bodies, bilateral hilar nodes, erythema nodosum, raised ACE and hypercalcaemia strongly suggest sarcoidosis, but none of these features is specific, and in India tuberculosis can produce non-caseating granulomas with a negative ZN stain. Steroids given for misdiagnosed TB can cause dissemination, so tissue should be sent for mycobacterial culture and CBNAAT, and fungal infection excluded, before treatment. Sarcoidosis remains a diagnosis of exclusion.
- A: The Kveim test is obsolete and unavailable.
- C: Isoniazid alone is wrong if TB is active; active disease must be ruled out first.
- D: Serum ACE is non-specific, and repeating it does nothing to exclude TB.
Remember this
Before steroids for presumed sarcoidosis in India, exclude TB on tissue with culture and CBNAAT; granulomas alone are not specific.
Question 5 · Easy
Two months after a renal transplant, a man on tacrolimus and mycophenolate has bloody diarrhoea. Colonic biopsy shows large cells in the endothelium and stroma with a single big intranuclear inclusion surrounded by a halo and small granular cytoplasmic inclusions. Which virus is responsible?
1. AEpstein-Barr virus
2. BAdenovirus
3. CHerpes simplex virus
4. DCytomegalovirus
Show answerHide answer
Answer: D · Cytomegalovirus
Enlarged cells (cytomegaly) with an owl's eye intranuclear inclusion and granular cytoplasmic inclusions in endothelial and stromal cells are diagnostic of cytomegalovirus. CMV colitis peaks 1-6 months after solid organ transplantation; IHC for CMV antigen confirms it, and IV ganciclovir is the treatment. HSV inclusions occur in squamous cells without cytomegaly.
- A: EBV causes post-transplant lymphoproliferative disease, not viral inclusions.
- B: Adenovirus gives smudgy nuclear inclusions in surface epithelium.
- C: HSV forms multinucleated cells with ground-glass nuclei, without cytomegaly or cytoplasmic inclusions.
Remember this
Owl's eye intranuclear plus cytoplasmic inclusions in enlarged endothelial cells mean CMV.
Question 6 · Medium
Oesophageal biopsies are taken from ulcers in a patient with AIDS and odynophagia. Which statements are correct? 1. HSV inclusions are seen in squamous cells at the ulcer edge. 2. CMV produces only intranuclear inclusions, never cytoplasmic ones. 3. CMV inclusions are found in endothelial and stromal cells of the ulcer base. 4. HSV causes cytomegaly of infected cells.
1. A2 and 4 only
2. B1 and 3 only
3. C1, 2 and 3 only
4. D1, 3 and 4 only
Answer and explanation in LearnFree account
Question 7 · Medium
In a brain biopsy from a man with AIDS, enlarged oligodendrocyte nuclei with ground-glass inclusions and bizarre astrocytes surround areas of demyelination. Which virus?
1. AJC polyomavirus
2. BHIV itself
3. CMeasles virus
4. DCytomegalovirus
Answer and explanation in LearnFree account
Question 8 · Easy
Which modified acid-fast stain, using a weaker decolouriser, best demonstrates Mycobacterium leprae in a skin biopsy?
1. AGrocott methenamine silver
2. BGiemsa stain
3. CAuramine-rhodamine stain
4. DFite-Faraco stain
Answer and explanation in LearnFree account
Question 9 · Medium
A resident compares intestinal ulcers seen at autopsy. Which statements are correct? 1. Typhoid ulcers lie along the long axis of the ileum over Peyer's patches. 2. Tuberculous ulcers are transverse (girdle-like). 3. The typhoid infiltrate is rich in neutrophils. 4. Healed typhoid ulcers commonly cause strictures.
1. A1, 2 and 3 only
2. B1, 3 and 4 only
3. C2 and 4 only
4. D1 and 2 only
Answer and explanation in LearnFree account
Question 10 · Hard
Four months into multidrug therapy for lepromatous leprosy, a young tailor in Odisha develops crops of painful red nodules on the face, arms and thighs, with fever, joint pains and tender ulnar nerves. Earlier skin lesions are unchanged, and he has taken his blister packs regularly. His bacterial index was 4+ at the start of treatment. Urine shows proteinuria and the ESR is 90 mm/h. Biopsy of a fresh nodule shows a neutrophil-rich infiltrate with vasculitis in the deep dermis and subcutis, among foamy macrophages containing fragmented bacilli. What is the immunological basis of this episode?
1. AIncreased cell-mediated immunity (type IV)
2. BDrug hypersensitivity to dapsone
3. CImmune complex deposition (type III)
4. DIgE-mediated mast cell release (type I)
Answer and explanation in LearnFree account
Question 11 · Easy
Excision biopsy of a matted cervical lymph node from a college student with evening fever and weight loss shows granulomas with central caseous necrosis, epithelioid cells and Langhans giant cells. Which stain should the pathologist request on this section to look for the organism?
1. AZiehl-Neelsen stain
2. BPeriodic acid-Schiff stain
3. CMucicarmine stain
4. DWarthin-Starry silver stain
Answer and explanation in LearnFree account
Question 12 · Easy
A boy from a village in Tamil Nadu who bathes in a common pond has a bleeding, strawberry-like polyp in the nose. Histology shows thick-walled sporangia packed with endospores in a vascular stroma. What is the organism?
1. AKlebsiella rhinoscleromatis
2. BRhinosporidium seeberi
3. CAspergillus flavus
4. DRhizopus arrhizus
Answer and explanation in LearnFree account
Question 13 · Medium
Black necrotic eschar on the palate and facial swelling develop in a man with uncontrolled diabetes (blood glucose 420 mg/dL, ketones positive) three weeks after he recovered from COVID-19 treated with high-dose steroids. A debrided tissue biopsy shows broad, ribbon-like, pauciseptate hyphae branching at right angles and invading blood vessels. Besides surgical debridement and correcting the ketoacidosis, which drug should be started?
1. AVoriconazole
2. BFluconazole
3. CLiposomal amphotericin B
4. DCaspofungin
Answer and explanation in LearnFree account
Question 14 · Medium
Lung biopsy in a neutropenic leukaemia patient shows narrow septate hyphae with regular acute-angle dichotomous branching invading vessels. Which fungus is this?
1. ACandida albicans
2. BRhizopus oryzae
3. CPneumocystis jirovecii
4. DAspergillus fumigatus
Answer and explanation in LearnFree account
Question 15 · Medium
Bronchoalveolar lavage from a man with HIV (CD4 count 80/µL) who has dry cough, breathlessness on exertion and bilateral ground-glass shadows shows foamy, honeycomb eosinophilic alveolar casts; GMS stain shows cup-shaped cysts like crushed ping-pong balls. His PaO2 on room air is 82 mmHg. Which drug is first-line treatment?
1. ACotrimoxazole
2. BGanciclovir
3. CClarithromycin
4. DFluconazole
Answer and explanation in LearnFree account
Question 16 · Medium
Violaceous plaques on the legs and palate of a man with untreated HIV are biopsied. Histology shows spindle cells forming slit-like vascular spaces with extravasated red cells, haemosiderin and hyaline globules. Which immunohistochemical marker confirms the diagnosis?
1. ACD34 alone
2. BFactor XIIIa
3. CEBV LMP-1
4. DHHV-8 LANA-1
Answer and explanation in LearnFree account
Question 17 · Medium
A barefoot farmer from Rajasthan has had a painless swelling of the right foot for 4 years with multiple sinuses discharging black grains. Crushed grains in KOH show broad septate hyphae with chlamydospores. X-ray shows cavities in the metatarsals. What is the most appropriate treatment?
1. APenicillin for 6 months
2. BDapsone and rifampicin
3. CCotrimoxazole with amikacin
4. DItraconazole with surgical excision
Answer and explanation in LearnFree account
Question 18 · Medium
Bone marrow aspirate of a labourer from Muzaffarpur, Bihar, with fever for 3 months, massive splenomegaly, darkened skin and pancytopenia: macrophages contain many small round to oval bodies, each with a nucleus and a rod-shaped kinetoplast, on Giemsa stain. The rK39 test is positive. What is the diagnosis?
1. ADisseminated histoplasmosis
2. BVisceral leishmaniasis
3. CToxoplasmosis
4. DChronic malaria with hypersplenism
Answer and explanation in LearnFree account
Question 19 · Hard
Lymph node biopsies from two patients with tuberculosis are compared. The first, with normal immunity, shows well-formed caseating granulomas with scanty bacilli. The second, with HIV and a CD4 count of 40/µL, shows sheets of necrosis and macrophages with poorly formed granulomas and numerous acid-fast bacilli. Which immune defect best explains the second pattern?
1. AExcess Th2 response with eosinophils
2. BDeficiency of the membrane attack complex
3. CFailure of neutrophil oxidative killing
4. DLoss of Th1 cells and IFN-gamma activation of macrophages
Answer and explanation in LearnFree account
Question 20 · Medium
CT abdomen of a farmer from West Bengal with fever, weight loss and postural hypotension shows bilateral bulky adrenal masses. Early-morning cortisol is low. CT-guided adrenal biopsy: sheets of macrophages packed with small (2-4 µm) oval yeasts with a clear halo, staining with GMS and PAS; no kinetoplast is seen. What is the most likely organism?
1. ALeishmania donovani
2. BHistoplasma capsulatum
3. CCryptococcus neoformans
4. DMycobacterium tuberculosis
Answer and explanation in LearnFree account
Question 21 · Easy
A CSF sample from a man with HIV (CD4 count 60/µL), headache for 3 weeks and raised opening pressure shows yeasts surrounded by a clear halo on India ink. A meningeal biopsy from a similar case stains the thick capsule bright red with mucicarmine. Which organism is it?
1. ACandida albicans
2. BCoccidioides immitis
3. CCryptococcus neoformans
4. DHistoplasma capsulatum
Answer and explanation in LearnFree account
Question 22 · Medium
Nasal biopsy from a woman with progressive, hard, non-ulcerated nasal swelling and crusting over a year: dense plasma cells with Russell bodies and many large vacuolated histiocytes containing gram-negative bacilli. Name the causative organism.
1. ARhinosporidium seeberi
2. BLeishmania tropica
3. CKlebsiella rhinoscleromatis
4. DMycobacterium leprae
Answer and explanation in LearnFree account
Question 23 · Medium
A veterinary student has had a tender axillary lymph node for 3 weeks, after a scratch on the forearm from a kitten that left a small papule. Node biopsy shows stellate microabscesses with central neutrophils, rimmed by palisading epithelioid histiocytes. ZN and PAS stains are negative. Which stain is most likely to show the organism?
1. AZiehl-Neelsen acid-fast stain
2. BWarthin-Starry silver stain
3. CMucicarmine stain
4. DGiemsa stain
Answer and explanation in LearnFree account
Question 24 · Hard
A man from Manipur with HIV (CD4 count 30/µL), who stopped ART a year ago, has fever, weight loss, Hb 8.4 g/dL, hepatosplenomegaly and many umbilicated papules on the face resembling molluscum contagiosum. A skin biopsy shows macrophages filled with small oval yeast-like cells; several are elongated with a central transverse septum, dividing by fission rather than budding. Culture at 25 °C grows a mould that releases a diffusible red pigment into the agar, and blood cultures grow the same organism. Chest X-ray shows diffuse small nodules. Which organism is responsible?
1. ALeishmania donovani
2. BCryptococcus neoformans
3. CTalaromyces marneffei
4. DHistoplasma capsulatum
Answer and explanation in LearnFree account
Question 25 · Hard
Duodenal biopsy from a man with HIV (CD4 count 25/µL), chronic diarrhoea, fever, weight loss and abdominal lymphadenopathy shows villi expanded by sheets of foamy macrophages in the lamina propria. The macrophages are strongly PAS-positive, and ZN staining shows them packed with acid-fast bacilli. There are no granulomas. Which organism is most likely?
1. AMycobacterium avium complex
2. BMycobacterium tuberculosis
3. CHistoplasma capsulatum
4. DTropheryma whipplei
Answer and explanation in LearnFree account

1 more Infectious disease pathology questions

Answer them one by one, keep your score and see your weak topics in Learn. Signed-out visitors try 25 per exam; sign in with Google to see them all.

Study Pathology

Infectious disease pathology

A painless, indurated ulcer on the penis of a truck driver has a clean base, and he has rubbery, non-tender inguinal nodes. A biopsy is taken because dark-ground microscopy is not available. Which histological pattern is most characteristic of the likely infection?

Two months after a renal transplant, a man on tacrolimus and mycophenolate has bloody diarrhoea. Colonic biopsy shows large cells in the endothelium and stroma with a single big intranuclear inclusion surrounded by a halo and small granular cytoplasmic inclusions. Which virus is responsible?

In a brain biopsy from a man with AIDS, enlarged oligodendrocyte nuclei with ground-glass inclusions and bizarre astrocytes surround areas of demyelination. Which virus?

Which modified acid-fast stain, using a weaker decolouriser, best demonstrates Mycobacterium leprae in a skin biopsy?

Excision biopsy of a matted cervical lymph node from a college student with evening fever and weight loss shows granulomas with central caseous necrosis, epithelioid cells and Langhans giant cells. Which stain should the pathologist request on this section to look for the organism?

A boy from a village in Tamil Nadu who bathes in a common pond has a bleeding, strawberry-like polyp in the nose. Histology shows thick-walled sporangia packed with endospores in a vascular stroma. What is the organism?

Lung biopsy in a neutropenic leukaemia patient shows narrow septate hyphae with regular acute-angle dichotomous branching invading vessels. Which fungus is this?

Violaceous plaques on the legs and palate of a man with untreated HIV are biopsied. Histology shows spindle cells forming slit-like vascular spaces with extravasated red cells, haemosiderin and hyaline globules. Which immunohistochemical marker confirms the diagnosis?

A barefoot farmer from Rajasthan has had a painless swelling of the right foot for 4 years with multiple sinuses discharging black grains. Crushed grains in KOH show broad septate hyphae with chlamydospores. X-ray shows cavities in the metatarsals. What is the most appropriate treatment?

A CSF sample from a man with HIV (CD4 count 60/µL), headache for 3 weeks and raised opening pressure shows yeasts surrounded by a clear halo on India ink. A meningeal biopsy from a similar case stains the thick capsule bright red with mucicarmine. Which organism is it?

Nasal biopsy from a woman with progressive, hard, non-ulcerated nasal swelling and crusting over a year: dense plasma cells with Russell bodies and many large vacuolated histiocytes containing gram-negative bacilli. Name the causative organism.