I need answers for... What are the causes of acute, subacute, and chronic fevers? What are the examples for continuous, remittent, intermittent, and relapsing type of fevers? In India, if you suspect... if there is fever, you have to suspect what and all diseases which are more common? If a patient presents with fever with ar- arthralgia, what are the differential diagnosis? If they're present with fever with rash, then what and all are the diagnosis? What is Jenvey's lesion? Fever with hepatosplenomegaly seen in which and all conditions? Uh, then I want about life cycle of malaria, abdominal TB. Where in all do we see fever with altered sensorium? What is leukoencephalopathy?

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Here is your comprehensive clinical reference covering all the topics you asked about:

Fever - Complete Clinical Overview

1. Causes of Acute, Subacute, and Chronic Fever

Acute Fever (< 2 weeks)

Infections: Most bacterial infections (pneumonia, UTI, cellulitis, meningitis), viral illnesses (influenza, dengue, COVID-19), malaria, typhoid (early phase), leptospirosis
Non-infectious: Drug fever, transfusion reactions, pulmonary embolism, deep vein thrombosis, acute myocardial infarction, hematoma, post-operative fever

Subacute Fever (2-6 weeks)

Infections: Infective endocarditis, brucellosis, tuberculosis (early), typhoid (prolonged), enteric fever, fungal infections, viral hepatitis
Non-infectious: Malignancy (lymphoma), connective tissue diseases (SLE, vasculitis), drug fever
Common in ICU: ~80% of febrile episodes are infectious - pneumonia, catheter-related infections

Chronic Fever (> 6 weeks / Fever of Unknown Origin)

Infections: Tuberculosis, brucellosis, deep-seated abscesses, infective endocarditis, HIV, fungal infections (histoplasmosis - classified by duration into acute/subacute/chronic)
Non-infectious: Malignancies (lymphoma, renal cell carcinoma, hepatocellular carcinoma), connective tissue diseases (SLE, Adult Still disease, vasculitis), granulomatous diseases (sarcoidosis, Crohn's)
Drug fever can occur at any duration

Sources: Goldman-Cecil Medicine; Histoplasmosis chapter, Red Book 2021

2. Types of Fever - Patterns with Examples

Type	Definition	Classic Examples
Continuous	Temperature stays elevated throughout 24 hours, does not touch normal; variation < 1°C	Typhoid fever (Salmonella typhi), lobar pneumonia, urinary tract infection
Remittent	Temperature remains elevated but touches near-normal values; variation > 1°C but does NOT reach normal	Infective endocarditis, many viral infections, brucellosis
Intermittent	Temperature spikes to fever then returns to NORMAL (afebrile) during the same day	Malaria (tertian = P. vivax/ovale every 48h; quartan = P. malariae every 72h), pyogenic abscess, septicemia, kala-azar (double daily spike = Pel-Ebstein not applicable here)
Relapsing / Periodic	Days of fever alternating with days of completely normal temperature	Borrelia relapsing fever, malaria (relapses from P. vivax/ovale hypnozoites), Pel-Ebstein fever in Hodgkin's lymphoma, brucellosis (undulant fever)

3. Fevers Common in India - What to Suspect

In the Indian subcontinent, the following should be strongly suspected in a febrile patient:

Infectious (most common):

Malaria (P. vivax most common; P. falciparum - severe/cerebral)
Typhoid / Enteric fever (Salmonella typhi/paratyphi)
Dengue fever (Aedes mosquito-borne)
Chikungunya (fever + severe arthralgia)
Leptospirosis (post-flood, occupational exposure)
Scrub typhus (Orientia tsutsugamushi; eschar is pathognomonic)
Rickettsial fever (spotted fevers, tick-borne)
Tuberculosis (pulmonary and extrapulmonary; chronic low-grade fever)
Kala-azar / Visceral leishmaniasis (Bihar, Jharkhand, Bengal, Assam endemic belt)
Brucellosis (cattle farming areas, dairy workers)
Viral hepatitis A/E (hepatitis with fever in endemic areas)
Japanese encephalitis (Culex mosquito; Bihar, UP, Assam)
Melioidosis (Northeast India, coastal areas)
Enteric fever-related complications

Non-infectious to consider:

Connective tissue diseases (SLE, adult Still's disease)
Lymphomas
Drug fever

4. Fever with Arthralgia - Differential Diagnosis

Diagnosis	Key Features
Chikungunya	Bilateral symmetrical, very severe joint pain (incapacitating); maculopapular rash; Aedes aegypti
Dengue	Bone-crushing myalgia + arthralgia; retro-orbital pain; thrombocytopenia
Acute Rheumatic Fever	Migratory polyarthritis; Jones criteria (major: carditis, chorea, erythema marginatum, subcutaneous nodules, arthritis)
Rheumatoid Arthritis (reactive/early)	Symmetrical small joint involvement; morning stiffness
Serum sickness / Drug reaction	Fever + arthralgia + rash + urticaria
Infective Endocarditis	Fever + arthralgia + cardiac murmur
Primary HIV seroconversion (ARS)	Fever, pharyngitis, lymphadenopathy, rash, arthralgia; resembles glandular fever
Viral hepatitis (HBV)	Serum sickness-like prodrome: fever + arthralgia + rash before jaundice
SLE	Non-erosive arthralgia, malar rash, multi-system involvement
Adult Still's disease	Daily spiking fever, evanescent salmon-colored rash, arthralgia
Lyme disease	Tick exposure; erythema migrans rash; migratory arthralgia, carditis, neuroborreliosis
Brucellosis	Undulant fever; occupational/dietary exposure; sacroiliitis

Sources: Fuster & Hurst's The Heart; Fitzpatrick's Dermatology; Goldman-Cecil Medicine

5. Fever with Rash - Differential Diagnosis

By Rash Type:

Maculopapular rash + fever:

Measles (cephalocaudal spread, Koplik spots)
Rubella (milder, lymphadenopathy)
Dengue
Chikungunya
Infectious mononucleosis (EBV)
Roseola infantum (HHV-6; rash appears as fever breaks)
Primary HIV (ARS)
West Nile virus
Zika virus
Parvovirus B19 (slapped cheek + lacy reticular rash)
Scarlet fever (sandpaper rash, strawberry tongue, desquamation of palms/soles)
Rocky Mountain spotted fever (centripetal spread, palms/soles involvement)
Ehrlichiosis
Drug reactions (exanthematous)
Kawasaki disease

Petechiae/Purpura + fever (EMERGENCIES):

Meningococcemia (Neisseria meningitidis) - non-blanching purpura, rapidly progressive; EMERGENCY
Rocky Mountain spotted fever (may progress to purpura)
Disseminated gonococcal infection
Infective endocarditis (petechiae + Osler nodes + Janeway lesions)
Dengue hemorrhagic fever
Thrombotic thrombocytopenic purpura (TTP)
Vasculitis (HSP/IgA vasculopathy)

Vesicular/Pustular rash + fever:

Varicella (chickenpox)
Herpes zoster (dermatomal)
Smallpox (all lesions in same stage - historical)
Herpes simplex
Enteroviral hand-foot-mouth disease

Other specific rashes:

Erythema migrans - Lyme disease
Erythema marginatum - Acute rheumatic fever
Butterfly (malar) rash - SLE
Erythema nodosum - TB, sarcoidosis, streptococcal infection, Crohn's
Eschar - Scrub typhus, rickettsial infections
Rose spots - Typhoid fever (abdomen/chest; faint salmon-colored)

Source: Goldman-Cecil Medicine, Textbook of Family Medicine, Harrison's Principles of Internal Medicine 22E

6. Janeway Lesions

Definition: Janeway lesions are non-tender, erythematous or hemorrhagic macular/papular lesions on the palms and soles, caused by septic emboli in infective endocarditis.

Key features:

Location: palms and soles (plantar aspect, thenar/hypothenar eminence)
Non-tender (unlike Osler nodes which are PAINFUL)
Caused by infected microemboli with microabscess formation
Associated with acute infective endocarditis (especially Staphylococcus aureus)

Comparison with Osler Nodes:

Feature	Janeway Lesions	Osler Nodes
Tenderness	Non-tender	Painful/tender
Location	Palms, soles	Fingertips, pulp of digits
Mechanism	Septic emboli (microabscesses)	Immune complex deposition
Association	Acute IE (Staph aureus)	Subacute IE (Strep viridans)

Other signs of infective endocarditis: Fever (80-90%), heart murmur (75-85%), splinter hemorrhages (subungual), Roth spots (retinal), conjunctival hemorrhages, petechiae.

Sources: Textbook of Family Medicine; Dermatology 2-Volume Set 5e; Braunwald's Heart Disease

7. Fever with Hepatosplenomegaly - Conditions

Infectious:

Malaria (P. vivax/falciparum - massive splenomegaly in chronic/hyperreactive malaria)
Kala-azar / Visceral Leishmaniasis (massive progressive splenomegaly; the largest spleens seen in clinical practice)
Typhoid fever (Salmonella; splenomegaly in 2nd-3rd week)
Infectious mononucleosis (EBV; teenager with sore throat + lymphadenopathy + hepatosplenomegaly)
Viral hepatitis (A, B, E)
Infective endocarditis (bacterial emboli)
Brucellosis
Leptospirosis (Weil's disease)
Schistosomiasis (portal hypertension, massive splenomegaly)
Miliary tuberculosis
Typhus/rickettsial disease
Cytomegalovirus (CMV)
HIV/AIDS

Non-infectious:

Lymphomas (Hodgkin's and Non-Hodgkin's)
Leukemias (CML - massive splenomegaly)
Hemolytic anemias (thalassemia, sickle cell)
Storage diseases (Gaucher's, Niemann-Pick)
Autoimmune diseases (SLE, Still's disease)
Sarcoidosis
Portal hypertension (cirrhosis - enlargement of both; liver may actually shrink in cirrhosis)

8. Life Cycle of Malaria

Life cycle of Plasmodium malaria parasite - human and mosquito stages

IN THE HUMAN HOST:

1. Exoerythrocytic (Liver) Phase:

Female Anopheles mosquito bites → injects sporozoites into bloodstream (Step 1)
Sporozoites travel to liver within 1 hour → enter hepatocytes
Develop into tissue schizonts (Step 4) → each releases up to 30,000 merozoites (Step 5)
Hypnozoites (Step 3): In P. vivax and P. ovale only - some sporozoites remain dormant in liver → can reactivate months/years later causing relapse

2. Erythrocytic Phase (symptomatic):

Merozoites invade RBCs (Step 6) → ring form → trophozoite (Step 9) → schizont (Step 10) → rupture releases new merozoites (Step 11)
Cycle duration: 48 hrs (P. falciparum, P. vivax, P. ovale) → tertian fever; 72 hrs (P. malariae) → quartan fever
Schizont rupture causes fever spikes (pyrogens released)

3. Gametocyte Phase:

Some merozoites develop into male and female gametocytes (Step 12) - taken up by mosquito

IN THE MOSQUITO HOST:

Gametocytes → gametes → fertilization → zygote (Step 14) → ookinete (Step 15) → oocyst on gut wall (Step 16) → rupture → sporozoites migrate to salivary gland (Step 1) → ready to infect next human

Clinically important species differences:

Feature	P. vivax	P. falciparum	P. malariae	P. ovale
Fever cycle	48h (tertian)	48h (malignant tertian)	72h (quartan)	48h
Hypnozoites (relapse)	YES	No	No	YES
Severe disease	Less common	Most dangerous	Rare	Rare
RBC preference	Reticulocytes	All RBCs	Old RBCs	Reticulocytes

Source: Goldman-Cecil Medicine 22E; Medical Microbiology 9e

9. Abdominal Tuberculosis

Definition: TB involving any abdominal organ, accounting for ~15% of extrapulmonary TB cases.

Forms:

Tuberculous lymphadenopathy - MOST COMMON form; mesenteric lymph nodes most frequently involved; can develop central caseation and calcification
Peritoneal TB - Three subtypes:
- Wet ascitic type (most common): large free or loculated ascites; exudative; high SAAG
- Fixed fibrotic type: omental/mesenteric involvement, matted bowel loops on imaging
- Dry plastic type: fibrous peritoneal reaction, nodules, adhesions
GI TB - Most commonly involves the ileocecal region (MC site), followed by the jejunum
- Morphological types: ulcerative, hypertrophic, stricturing
- Difficult to distinguish from Crohn's disease
Visceral TB - Solid organs; genitourinary most frequent

Clinical Features:

Abdominal pain (most common), fever, weight loss (present for months)
Right lower quadrant mass in ~25%
Ascites on cross-sectional imaging strongly suggests abdominal TB over Crohn's

Key distinguishing features from Crohn's:

TB: transverse ulcers, patulous ileocecal valve, ascites, granulomas with caseation (>400 µm, large giant cells)
Crohn's: left colonic involvement, longitudinal ulcers, cobblestoning, skip lesions, rectal involvement

Histology: Caseating granulomas (coalescent, >400 µm, large giant cells); AFB staining, PCR, or culture confirms

Diagnosis: High suspicion in risk groups (immigrants from endemic areas, HIV, malnourished). Anti-TNF therapy for Crohn's can worsen unrecognized TB - must rule out TB before starting biologics.

Source: Yamada's Textbook of Gastroenterology 7e; Grainger & Allison's Diagnostic Radiology

10. Fever with Altered Sensorium - Where We See It

This is a serious clinical presentation. Key conditions:

Infections of CNS:

Bacterial meningitis (N. meningitidis, S. pneumoniae, L. monocytogenes) - fever + neck stiffness + altered sensorium (triad)
Viral encephalitis (Herpes simplex - most common treatable cause; Japanese encephalitis in India; West Nile)
Cerebral malaria (P. falciparum - parasitized RBCs occlude cerebral vessels; severe manifestation)
Tubercular meningitis (subacute onset, cranial nerve palsies)
Bacterial brain abscess (focal signs + fever)
Cerebral toxoplasmosis (HIV patients)
Rickettsial encephalitis (Scrub typhus with meningoencephalitis)

Systemic infections with CNS involvement:

Leptospirosis (Weil's disease) - encephalitis, altered sensorium, psychosis, seizures, hemiplegia - quoted directly from Kaplan & Sadock's Comprehensive Textbook of Psychiatry
Typhoid encephalopathy ("muttering delirium" - 2nd-3rd week)
Septic encephalopathy (any severe sepsis - multiorgan dysfunction)
Dengue encephalitis (rare manifestation of dengue)
Rabies (hydrophobia, aerophobia, agitation)
Neuro-syphilis (chronic, VDRL positive)
Plasmodium falciparum - cerebral malaria (specific to P. falciparum)
Polyarteritis Nodosa (PAN) - catastrophic intracranial hemorrhage with altered sensorium has been described (especially pediatric PAN)

Non-infectious:

Liver failure (hepatic encephalopathy - asterixis, elevated ammonia)
Uremic encephalopathy
Anti-NMDA receptor encephalitis (autoimmune; fever + psychiatric + movement disorder)
Heat stroke (exertional or classic)
Drug/toxin ingestion
Metabolic derangements (hyponatremia, hypoglycemia, DKA)

Sources: Bradley and Daroff's Neurology; Kaplan & Sadock's Comprehensive Textbook; Goldman-Cecil Medicine

11. Leukoencephalopathy

Progressive Multifocal Leukoencephalopathy (PML)

Definition: PML is a demyelinating brain disease caused by lytic replication of JC polyomavirus in oligodendrocytes (the cells that produce myelin) in subcortical white matter and, rarely, gray matter neurons.

Pathogen: JC polyomavirus (human polyomavirus 2)

Pathobiology:

JC virus replicates in oligodendrocytes → cell lysis → loss of myelin sheaths
Affected oligodendrocytes: enlarged nuclei with eosinophilic intranuclear inclusions
Lesions start in subcortical white matter, less commonly cerebellum or basal ganglia
As demyelination expands: lesions range from <1 mm to several cm; multiple zones coalesce

Epidemiology:

General population: ~0.3 per 100,000 person-years (North America/Europe)
HIV/AIDS (pre-ART era): ~2.4 per 1,000 patient-years; prevalence 1-7%
Natalizumab (for MS): ~2.13 per 1,000 patient-years; rises to 11.1 per 1,000 in JC-seropositive patients treated >24 months
Also seen with: lymphoproliferative malignancies, other immunosuppressive biologics, idiopathic CD4 lymphocytopenia

Predisposing conditions (any state of impaired T- and B-cell immunity):

HIV/AIDS (most common historically)
Hematologic malignancies (lymphoma, CLL, multiple myeloma)
Organ transplant recipients (on immunosuppressants)
Natalizumab therapy (multiple sclerosis)
Other monoclonal antibodies (rituximab, efalizumab)
Sarcoidosis

Clinical Manifestations:

Progressive motor weakness (most common)
Speech abnormalities, cognitive deficits
Headache, ataxia, aphasia, cranial nerve deficits
Visual disturbances (optic agnosia, cortical blindness, oculomotor abnormalities)
Seizures (more common with gadolinium-enhancing cortical lesions)
Sensory deficits of hands (parietal involvement)

Diagnosis: MRI (T2/FLAIR hyperintense non-enhancing white matter lesions), JC virus PCR in CSF

Treatment:

No specific anti-JC viral therapy proven effective
For HIV patients: start/optimize antiretroviral therapy → immune reconstitution
Withdraw offending immunosuppressive agent (e.g., stop natalizumab, plasmapheresis to accelerate removal)
Risk of IRIS (immune reconstitution inflammatory syndrome) when immunity is restored

Prevention: In HIV/AIDS, ART reducing HIV to undetectable levels has dramatically reduced PML incidence.

Source: Goldman-Cecil Medicine International Edition; Firestein & Kelley's Textbook of Rheumatology; Bradley and Daroff's Neurology in Clinical Practice

Quick Summary Mnemonics

Fever patterns - "CRIR":

Continuous = Typhoid, lobar pneumonia
Remittent = Infective endocarditis, viral fevers
Intermittent = Malaria, pyogenic abscess
Relapsing = Borrelia, Hodgkin's (Pel-Ebstein), brucellosis

Fever + Rash EMERGENCIES to rule out first:

Meningococcemia (non-blanching petechiae/purpura → septic shock)
Rocky Mountain Spotted Fever (petechiae on palms/soles spreading centrally)
Toxic Shock Syndrome (Staph/Strep)
Staphylococcal Scalded Skin Syndrome

Janeway vs Osler:

Janeway = No pain, on palms/soles = Acute IE (Staph aureus)
Osler = Ouchy/painful, on digits = Subacute IE (Strep viridans)

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