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3rd December Theory Class


🌡️ Viral Exanthems — Overview

Viral exanthems = widespread rashes caused by viral infections, often accompanied by fever, malaise, respiratory or GI symptoms.
They are common in pediatrics, but many affect adults too.

Below is a structured, easy-to-revise list.

👶 CLASSICAL CHILDHOOD VIRAL EXANTHEMS

1️⃣ Measles (Rubeola)

Prodrome: 3 Cs — Cough, Coryza, Conjunctivitis, + photophobia
Pathognomonic: Koplik spots (enanthem on buccal mucosa)
Rash:

  • Begins at hairline → face → trunk → limbs (cephalocaudal, centrifugal)

  • Brick-red, maculopapular, may become confluent
    Complication: SSPE, pneumonia

2️⃣ Rubella (German measles)

Prodrome: Mild fever
Lymphadenopathy: Postauricular + Suboccipital
Rash:

  • Pink, maculopapular

  • Fades quickly (within 3 days)
    Enanthem: Forchheimer spots (soft palate petechiae)

3️⃣ Roseola Infantum (HHV-6/7)

Key: High fever → subsides → rash appears
Rash:

  • Pink macules, trunk > neck/face

  • Non-pruritic
    Age: <2 years

4️⃣ Erythema Infectiosum (Parvovirus B19)

Slapped-cheek appearance
Then → Lacy, reticular rash on extremities and trunk
Complications:

  • Aplastic crisis in hemolytic anemia

  • Hydrops fetalis (pregnancy)

5️⃣ Varicella (Chickenpox, VZV)

Hallmark: Lesions in different stages simultaneously

  • Macule → Papule → Vesicle → Pustule → Crust
    Description:

  • “Dew-drop on rose petal” vesicles
    Distribution: centripetal (trunk > limbs)

🦠 OTHER VIRAL EXANTHEMS / SKIN LESIONS

🔸 Hand-Foot-Mouth Disease (Coxsackie A16)

Oral ulcers + vesicles on palms/soles/buttocks
Common in <5 years
Variant: Coxsackie A6 → severe painful lesions

🔸 Molluscum Contagiosum (Poxvirus)

Umbilicated, pearly papules
Seen in children, sexually active adults, immunocompromised
In HIV — may be extensive, atypical

🔸 Herpes Simplex (HSV-1/2)

Grouped vesicles on erythematous base
Painful
Recurrent
HSV-1: orolabial
HSV-2: genital

🔸 Herpes Zoster (Shingles)

Reactivation of VZV
Unilateral, dermatomal, does not cross midline
Pain precedes rash
Complication: post-herpetic neuralgia

🔸 Gianotti-Crosti Syndrome (EBV, Hep B, others)

Infants/children
Monomorphic, flat-topped papules on face, limbs, buttocks
Relative trunk sparing

🔸 Pityriasis Rosea (HHV-7 association)

Herald patch → after days →
“Christmas-tree pattern” lesions on trunk
Oval, salmon-colored patches with collarette scaling
(Itching common)

🧪 High-Yield Clinical Differentiation Table

Disease Key Rash Features Other clues
Measles Brick-red, confluent maculopapular Koplik spots, 3Cs
Rubella Fine pink macules Postauricular LAD
Roseola Rash after fever subsides High fever in infants
Parvovirus B19 Slapped cheek + lacy rash Aplastic crisis
Varicella Multiple stages at one time Very itchy, trunk predominant
HFMD Vesicles mouth + palms/soles Coxsackie virus
Molluscum Umbilicated papules Poxvirus
HSV Grouped vesicles Recurrent, painful
Zoster Dermatomal vesicles Adult, painful
Pityriasis rosea Herald patch + tree pattern Young adults


APPROACH TO DIFFERENT TYPES OF FEVER

(General Medicine – MBBS/AIIMS Standard)

1. Start With KEY HISTORY POINTS

  • Duration: Acute (<7 days), Subacute (7–14 days), Chronic (>14 days)

  • Pattern: Continuous / Remittent / Intermittent / Pel-Ebstein / Relapsing

  • Associated symptoms: rash, cough, urinary symptoms, abdominal pain, joint pain

  • Travel history

  • Drug history

  • Animal exposure, mosquito exposure

  • Immunocompromised state

  • Recent hospitalization (nosocomial fever)

  • Weight loss, night sweats

2. FEVER PATTERNS & DIFFERENTIALS

A. Continuous Fever

Temperature remains above normal throughout the day and fluctuations <1°C.

Causes

  • Lobar pneumonia

  • Typhoid (classically step-ladder → then continuous)

  • UTI / Pyelonephritis

  • Meningitis

  • Malaria (in P. falciparum severe cases)

Clinical Clue: Patient looks ill, toxic; no afebrile period.

B. Remittent Fever

Temperature fluctuates >1°C daily but never returns to normal.

Causes

  • Infective endocarditis

  • Brucellosis

  • Tuberculosis

  • Viral infections (influenza, dengue early phase)

Clinical Clue: Persistent fever with daily variation.

C. Intermittent Fever

Fever spikes separated by normal temperature periods.

Patterns

  1. Quotidian (daily) – e.g., sepsis, Still’s disease

  2. Tertian (every 48 hrs) – P. vivax, P. falciparum

  3. Quartan (every 72 hrs) – P. malariae

Classical Cause: Malaria

D. Pel-Ebstein Fever

Fever for 3–10 days → afebrile for 3–10 days (cyclical).

Cause: Hodgkin lymphoma
Rare but exam favourite.

E. Relapsing Fever

Fever for 2–7 days → afebrile for a week → fever returns.

Causes

  • Borrelia (tick-borne relapsing fever)

  • Louse-borne relapsing fever

  • Malaria (P. vivax/ovale relapse due to hypnozoites)

F. Saddleback Fever

Fever → remits → returns again (saddle shape).

Cause: Dengue (classic pattern around day 3–5)

3. APPROACH BASED ON DURATION

A. Acute Fever (<7 days)

Think common infections:

  • URTI/LRTI

  • Dengue, Chikungunya

  • Malaria

  • Leptospirosis

  • Scrub typhus

  • Gastroenteritis

  • UTI
    Investigations

  • CBC with differential

  • RFT, LFT

  • Rapid malaria test/peripheral smear

  • Dengue NS1

  • Urine R/M

  • CXR (if respiratory symptoms)

B. Subacute Fever (7–14 days)

Think:

  • Enteric fever

  • Viral hepatitis

  • Complicated malaria

  • Abscesses

  • Endocarditis (subacute)

C. Chronic Fever (>14 days)

Think:

  • Tuberculosis

  • HIV

  • Malignancy (lymphoma)

  • Autoimmune diseases (SLE, RA, vasculitis)

  • Subacute bacterial endocarditis

  • Liver abscess

  • Osteomyelitis

4. SPECIAL TYPES OF FEVER

A. Fever with Rash

  • Measles – Koplik spots, cephalocaudal rash

  • Rubella – post-auricular lymphadenopathy

  • Dengue – islands of white in red

  • Meningococcemia – purpura

  • Rickettsial infections – eschar + rash

B. Fever with Rigors

Rigors suggest bacteremia:

  • UTI/pyelonephritis

  • Malaria

  • Liver abscess

  • Pneumonia with bacteremia

  • Sepsis

C. Fever with Bradycardia (Relative bradycardia – Faget sign)

  • Typhoid

  • Dengue

  • Yellow fever

  • Drug fever

  • Legionella

D. Fever with Jaundice

  • Viral hepatitis

  • Leptospirosis

  • Severe malaria

  • Sepsis with cholestasis

  • Hemolysis

E. Fever in Returning Traveler

  • Malaria

  • Dengue

  • Zika

  • Chikungunya

  • Typhoid

  • Schistosomiasis

5. BASIC INVESTIGATIONS IN ANY UNEXPLAINED FEVER

  • CBC

  • ESR/CRP

  • RFT, LFT

  • Urine R/M + Culture

  • Blood cultures (multiple sets)

  • Chest X-ray

  • Peripheral smear for malaria

  • Ultrasound abdomen (if persistent)

  • HIV, TB screening if indicated

6. FEVER OF UNKNOWN ORIGIN (FUO)

Fever >38.3°C for >3 weeks & no diagnosis after 1 week evaluation.

Major Causes

  1. Infections – TB, abscesses, endocarditis

  2. Malignancy – lymphoma, leukemia

  3. Autoimmune – SLE, RA, vasculitis

  4. Miscellaneous – drug fever, thyroiditis

  5. Factitious fever

7. Red Flags (Urgent Attention)

  • Hypotension

  • Altered sensorium

  • Petechiae/purpura

  • Severe dehydration

  • Respiratory distress

  • Neck rigidity

  • Severe abdominal tenderness

  • Oliguria


📌 TYPES OF FRACTURES

1️⃣ Based on Line/Pattern of Break

Type Description Key Features
Transverse fracture Horizontal break Direct blow
Oblique fracture Angled fracture Indirect trauma
Spiral fracture Spiral line around shaft Torsional injury
Comminuted fracture >2 fragments High-energy trauma
Segmental fracture Two fracture lines with an isolated segment Severe energy

2️⃣ Based on Completeness

Type Description
Complete fracture Bone broken through entire width
Incomplete fracture Common in children (greenstick, torus/buckle)
Greenstick Cortex breaks on one side, bends on the other
Torus/Buckle Cortex buckles → stable

3️⃣ Based on Displacement

  • Non-displaced

  • Displaced → angulation, rotation, shortening

  • Impacted → one fragment driven into the other

4️⃣ Based on Soft Tissue Injury

Type Features
Closed fracture No communication with outside
Open (compound) Wound connects to fracture; risk of infection (Gustilo–Anderson classification)

5️⃣ Special Fracture Types

Type Features
Avulsion fracture Tendon/ligament pulls bone fragment
Stress fracture Repeated microtrauma; shin splints
Pathological fracture Pre-existing disease (tumor, osteoporosis)
Physeal fracture In children; classified by Salter–Harris
Intra-articular fracture Enters joint — requires anatomical reduction

📌 TYPES OF BONE HEALING

Bone heals in two major pathways:

1️⃣ Primary Bone Healing (Direct Healing)

Occurs when:

  • Fracture ends are perfectly reduced

  • Rigid fixation & compression (e.g., plating)

  • Gap < 0.01 mm; strain < 2%

Mechanism

  • No visible callus

  • Cutting cones by osteoclasts & refilled by osteoblasts

  • Haversian remodeling

Types of Primary Healing

  1. Contact healing → direct bridging of Haversian systems

  2. Gap healing → small gap → filled by lamellar bone → remodeled

Clinical Relevance

  • Ideal in articular fractures

  • Needs absolute stability

2️⃣ Secondary Bone Healing (Indirect Healing)

Occurs in most fractures (plaster, external fixators, IM nails)

Stages of Secondary Healing

  1. Haematoma formation (Day 1–3)

    • Clot, inflammatory cells

  2. Soft callus (Fibrocartilaginous) (1–3 weeks)

    • Granulation tissue → fibrocartilage

  3. Hard callus (3–12 weeks)

    • Woven bone deposition

  4. Remodeling (Months–years)

    • Woven → lamellar

    • Wolff’s law: bone aligns along stress lines

Features

  • Visible callus on X-ray

  • Requires relative stability

  • Can tolerate higher strain (up to 10%)

🔑 Primary vs Secondary Healing (Exam Mnemonic)

Feature Primary Secondary
Stability Absolute Relative
Callus ❌ Absent ✔️ Present
Occurs with Plating Casting, IM nail
Strain tolerance Very low Moderate
Speed Slower initially Faster callus formation
Ideal for Intra-articular Diaphyseal


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