Most probable diagnosis:

• Systemic-onset Juvenile Idiopathic Arthritis (SoJIA) / Still's disease (Systemic JRA)

Expected systemic clinical findings:

• Hepatosplenomegaly
• Generalized lymphadenopathy
• Serositis (pericarditis, pleuritis, peritonitis / serous cavity effusions)
• Evanescent, salmon-pink macular rash (accompanies fever spikes)
• Myalgias, arthralgias, and polyserositis

Value of serology in diagnosis:

• Antinuclear antibodies (ANA): Usually negative
• Rheumatoid Factor (RF): Usually negative
• Markedly elevated inflammatory markers (ESR, CRP, serum ferritin, leukocytosis, thrombocytosis)

Steps in management:

• First-line: NSAIDs (e.g., indomethacin, naproxen)
• Systemic Corticosteroids: Oral prednisolone or IV pulse methylprednisolone for severe systemic illness/serositis
• Disease-Modifying Antirheumatic Drugs (DMARDs): Methotrexate, Leflunomide
• Biologic agents:
  • IL-1 antagonists (Anakinra, Canakinumab)
  • IL-6 receptor antagonists (Tocilizumab)
  • TNF-alpha inhibitors (Etanercept, Infliximab, Adalimumab) for persistent arthritis

Prognostic factors:

• Number and severity of joint involvement (polyarticular extension)
• Persistent systemic inflammation / persistent thrombocytosis or leukocytosis
• Development of Macrophage Activation Syndrome (MAS)
• Early radiographic joint damage / persistent active disease at 6–12 months

Likely arthritis:

• Oligoarticular (Pauciarticular) JIA Type 1 (involves $\le 4$ joints, early onset, female predominance, ANA positive)

Complication to anticipate:

• Chronic anterior uveitis (iridocyclitis) — usually asymptomatic/insidious; requires regular slit-lamp screening to prevent visual impairment/blindness

Type of JRA with HLA-B27 positivity:

• Enthesitis-Related Arthritis (ERA) / Oligoarticular JIA Type 2 (typically older boys, axial/lower limb involvement)

Diagnosis for Q4:

• Macrophage Activation Syndrome (MAS) / Secondary HLH

Drug indicated in MAS:

• Cyclosporine (along with high-dose pulse IV Methylprednisolone; Anakinra/biologics in refractory cases)

Diagnosis:

• Neonatal Lupus Erythematosus (NLE) with Congenital Complete Heart Block (CCHB)

Clinical condition in mother:

• Systemic Lupus Erythematosus (SLE), Sjögren's syndrome, or undifferentiated autoimmune connective tissue disease (may be completely asymptomatic carrier of autoantibodies)

Prognosis of skin and cardiac disease:

• Skin lesions: Benign and transient; resolve spontaneously within 6 months as transplacentally acquired maternal IgG antibodies clear from neonatal circulation.
• Cardiac disease: Congenital heart block is irreversible and permanent (often requires permanent pacemaker placement).

Earliest antenatal diagnosis and test:

• At 16–18 weeks of gestation
• Test: Fetal echocardiography (evaluates fetal heart rate, PR interval, and rhythm) and Maternal serum anti-Ro/SSA & anti-La/SSB antibody titers

Antenatal maternal treatment:

• Fluorinated corticosteroids (Dexamethasone or Betamethasone) that cross the placenta; IVIG; plasmapheresis

Risk of recurrence in next pregnancy:

• Approximately 15–20% (increases to ~50% after two affected infants)

Probable diagnosis & Diagnostic criteria:

• Diagnosis: Henoch-Schönlein Purpura (HSP) / IgA Vasculitis
• Criteria (EULAR/PRINTO/PRES):
  • Mandatory criterion: Palpable purpura (non-thrombocytopenic, predominantly lower extremities/buttocks)
  • Plus at least ONE of the following:
    1. Diffuse abdominal pain
    2. Predominant IgA deposition on histopathology / immunofluorescence
    3. Arthritis (acute) or arthralgia
    4. Renal involvement (hematuria and/or proteinuria)

Indication for systemic steroids:

• Severe, debilitating abdominal pain / GI bleeding / bowel ischemia / intussusception
• Severe scrotal swelling/orchitis
• Severe renal involvement (crescentic HSP nephritis)
• Pulmonary hemorrhage or CNS vasculitis

Importance of monitoring urine protein:

• To monitor for HSP nephritis, which can develop or progress up to 6 months after disease onset. Early detection and treatment of persistent proteinuria/nephritis prevents progressive renal impairment.

Drug for chronic/refractory lesions:

• Dapsone (or colchicine)

Two small-vessel vasculitides:

• Granulomatosis with polyangiitis (GPA / Wegener's)
• Eosinophilic granulomatosis with polyangiitis (EGPA / Churg-Strauss)
• Microscopic polyangiitis (MPA)

Probable diagnosis:

• Kawasaki Disease (Mucocutaneous Lymph Node Syndrome)

Diagnostic criteria (Classic Kawasaki Disease):

• High-grade fever for $\ge 5$ days plus at least 4 of the 5 principal clinical criteria:
  1. Bilateral bulbar conjunctival injection without exudate
  2. Erythema and cracking of lips, strawberry tongue, erythema of oral and pharyngeal mucosa
  3. Polymorphous rash (maculopapular, erythema multiforme-like, or scarlatiniform)
  4. Changes in extremities: Acute erythema and edema of hands/feet, subacute periungual desquamation
  5. Cervical lymphadenopathy (usually unilateral, $\ge 1.5\text{ cm}$)

ECHO criteria:

• Z-score of LAD (Left Anterior Descending) or RCA (Right Coronary Artery) $\ge 2.5\text{ SD}$
• Perivascular brightness/cuffing
• Lack of normal tapering of coronary arteries
• Decreased left ventricular systolic function
• Mitral regurgitation / pericardial effusion

Differential diagnoses (DDs):

• Scarlet fever
• Staphylococcal Scalded Skin Syndrome (SSSS) / Toxic Shock Syndrome (TSS)
• Toxic Epidermal Necrolysis (TEN) / Stevens-Johnson Syndrome (SJS)
• Measles
• Rocky Mountain spotted fever
• Multisystem Inflammatory Syndrome in Children (MIS-C)
• Systemic JIA

Treatment:

• IVIG: $2\text{ g/kg}$ single IV infusion given over 10–12 hours
• High-dose Aspirin: $80\text{–}100\text{ mg/kg/day}$ in 4 divided doses until child is afebrile for 48–72 hours
• Low-dose Aspirin: $3\text{–}5\text{ mg/kg/day}$ once daily for 6–8 weeks (continued indefinitely if coronary aneurysms develop)
• Corticosteroids / Infliximab / Anakinra in IVIG-resistant Kawasaki disease

Follow-up plan (AHA Risk Stratification):

Probable diagnosis:

• Post-infectious Reactive Arthritis (Reiter's Syndrome)

HLA association:

• HLA-B27; positive in ~75% of affected patients

Causative agents:

• Bacteria: Campylobacter jejuni, Salmonella enterica, Shigella flexneri, Yersinia enterocolitica, Chlamydia trachomatis
• Viruses: Cytomegalovirus (CMV), Varicella Zoster Virus (VZV), Herpes Simplex Virus (HSV), Rubella, Parvovirus B19

Prognosis:

• Good; usually resolves completely within 3–6 months without long-term joint damage or permanent sequelae.

Diagnosis:

• Systemic Lupus Erythematosus (SLE)

Investigations to confirm diagnosis:

• Anti-dsDNA antibody: High specificity for SLE; correlates with disease activity and renal involvement
• Anti-Smith (anti-Sm) antibody: Most specific antibody for SLE
• ANA (Antinuclear antibody): Highly sensitive screening test
• Serum complement levels ($C_3,C_4,C{H}_{50}$): Decreased in active disease / flare
• Complete blood count & Urinalysis: Leukopenia, thrombocytopenia, proteinuria, active urinary casts

4 drugs that lead to drug-induced lupus (DIL):

• S - Sulfonamides / Sulfasalazine
• H - Hydralazine
• I - Isoniazid (INH)
• P - Procainamide / Penicillamine

Treatment options:

• Mild/Skin/Joint disease: Hydroxychloroquine (HCQ), NSAIDs, low-dose corticosteroids
• Severe/Organ-threatening (Lupus nephritis, CNS lupus):
  • Pulse IV Methylprednisolone followed by high-dose oral corticosteroids
  • Cyclophosphamide or Mycophenolate Mofetil (MMF)
  • Azathioprine, Methotrexate
  • Biologics: Rituximab (anti-CD20), Belimumab (anti-BAFF)

HLA associations:

• HLA-DR2, HLA-DR3, HLA-B8

Probable diagnosis:

• Juvenile Dermatomyositis (JDM)

Signs shown:

• Hand sign shown in picture: Gottron papules (violaceous, scaly papules over metacarpophalangeal and interphalangeal joints)
• Facial signs: Heliotrope rash (violaceous reddish-purple discoloration of upper eyelids with periorbital edema) and malar erythema

Serum enzyme levels to order:

• Creatine Phosphokinase (CPK)
• Serum Glutamic Oxaloacetic Transaminase (SGOT / AST)
• Lactate Dehydrogenase (LDH)
• Aldolase

Antibodies present in serum:

• Myositis-specific antibodies (Anti-TIF1-gamma / p155/140, Anti-NXP-2 / MJ, Anti-MDA5)
• Myositis-associated antibodies (Anti-RNP, Anti-PM/Scl, Anti-Ro)
• ANA (positive in 70–80%)

Drug for skin lesions, dose, and side effects:

• Drug: Hydroxychloroquine
• Dose: $4\text{–}6\text{ mg/kg/day}$ PO once daily (max $400\text{ mg/day}$)
• Side effects: Retinopathy (maculopathy / bull's eye retinopathy, color vision impairment), gastrointestinal upset, skin pigmentation. Requires periodic ophthalmological monitoring.

Probable diagnosis:

• Takayasu Arteritis (Pulseless Disease / Non-specific Aortoarteritis)

Most common artery involved:

• Aorta and its primary branches (subclavian arteries, carotid arteries, renal arteries)

Diagnostic criteria (EULAR/PRINTO/PRES Criteria):

• Mandatory: Angiographic abnormalities (conventional, CT, or MR angiography) of the aorta or its main branches (stenosis, occlusion, or aneurysm)
• Plus at least ONE of the following:
  1. Pulse deficit or claudication of an extremity
  2. Systolic blood pressure discrepancy $>10\text{ mmHg}$ between limbs
  3. Bruits over aorta or its major branches
  4. Hypertension (compared with age- and height-appropriate norms)
  5. Elevated acute phase reactants (ESR $\ge 20\text{ mm/hr}$ or elevated CRP)

Prognosis:

• Variable; ~20% have a monophasic, self-limiting course, but the majority (~80%) have a chronic relapsing or progressive disease course requiring long-term immunosuppressive therapy. Morbidity is determined by vascular complications (hypertension, retinopathy, stroke, heart failure, renal impairment).