Diseases & syndromes study sheet
| Disease | Classification | Lab and identification clues | High-yield clue | Associations |
|---|---|---|---|---|
| AIDS | Acquired immunodeficiency syndrome; Retrovirus (HIV) end-stage; Profound CD4 T-cell depletion; Blood, sexual, and perinatal spread | CD4 count below 200 cells/uL threshold vocabulary; HIV viral load concept; AIDS-defining illness list vocabulary | A CD4 count below 200 cells/uL, or an AIDS-defining opportunistic illness, marks progression from HIV to AIDS. | Opportunistic infections: PCP, cryptococcal meningitis, toxoplasmosis, esophageal candidiasis; Kaposi sarcoma (HHV-8) association; At-risk exposures: unprotected sex, shared needles, perinatal; Wasting and constitutional-symptom vocabulary |
| Amebiasis | Protozoal enteric syndrome; Entamoeba histolytica infection; Fecal-oral cyst ingestion; Invasive and inflammatory | Trophozoites with ingested red cells (erythrophagocytosis) vocabulary; Flask-shaped colonic ulcer vocabulary; Serology and stool antigen concept | Bloody dysentery with flask-shaped colonic ulcers and a possible right-upper-quadrant 'anchovy-paste' liver abscess is the classic amebiasis clue. | Transmission: fecally contaminated food/water and oral-anal contact; Amebic dysentery with bloody stools and abdominal pain; Amebic liver abscess ('anchovy paste') vocabulary; Endemic where sanitation is poor / tropical regions |
| Bacterial meningitis | CNS syndrome; Age-stratified organism patterns; Acute vs chronic framing; Pyogenic (bacterial) vs aseptic (viral) contrast | CSF with high neutrophils, low glucose, high protein vocabulary; Nuchal rigidity, Kernig and Brudzinski sign terms; CSF Gram stain and culture concept; Petechial/purpuric rash association with meningococcus | Fever, headache, and nuchal rigidity with a neutrophil-rich, low-glucose CSF profile is the core study picture. | Neonates: group B Strep, E. coli, Listeria vocabulary; Older children/adults: pneumococcus and meningococcus; College-dorm outbreak and vaccine public-health framing; Respiratory-droplet transmission for meningococcus |
| Botulism | Neuromuscular toxin syndrome; Flaccid (descending) paralysis pattern; Forms: foodborne, infant, wound, adult intestinal; Reportable public-health framing | Descending paralysis: cranial nerves first vocabulary; Bulbar signs: diplopia, ptosis, dysarthria, dysphagia terms; Infant form linked to honey and floppy-baby, constipation vocabulary; Toxin blocks acetylcholine release concept | Symmetric descending flaccid paralysis starting with cranial nerves (diplopia, ptosis, dysphagia) is the classic botulism clue. | Foodborne form from improperly canned low-acid foods; Infant (intestinal) form is the most common U.S. form; Wound form associated with injection drug use; No fever and preserved sensation as distinguishing framing |
| Candidiasis / thrush | Fungal (yeast) syndrome; Candida (usually C. albicans); Mucocutaneous and opportunistic; Endogenous normal-flora overgrowth | Scrapeable white pseudomembrane vocabulary; KOH prep budding yeast with pseudohyphae vocabulary; Germ tube test link (C. albicans) | White curd-like oral plaques that scrape off to leave a red base is thrush, a clue pointing to infancy, inhaled steroids, or immunosuppression. | Triggers: infancy, antibiotics, inhaled steroids, uncontrolled diabetes; Esophageal candidiasis is AIDS-defining; Vulvovaginal 'yeast infection' vocabulary; Invasive candidemia in ICU and catheter settings |
| Cellulitis | Skin and soft-tissue syndrome; Non-purulent (streptococcal) vs purulent (staphylococcal) patterns; Superficial dermal vs deeper fascial contrast; Community vs MRSA-associated framing | Clinical erythema, warmth, swelling, tenderness vocabulary; Ill-defined non-elevated borders (vs sharply raised erysipelas) description; Purulence/abscess suggesting Staphylococcus aureus; Blood cultures usually low-yield concept | Warm, tender, spreading erythema with indistinct borders is the classic cellulitis recognition clue. | Skin-barrier breaks: cuts, tinea, ulcers as entry points; Streptococcus pyogenes and Staphylococcus aureus most common; At-risk framing: edema, diabetes, venous insufficiency; Distinction from rapidly progressive necrotizing infection |
Assembled from the free PetriKey reference. Every row is published in full on its own reference page, with that page's own sources. Educational study reference only - not medical advice, and not for diagnosis, treatment, dosing, specimen handling, or any clinical decision-making.