What is the likely diagnosis and cause of intermittent hypertension in a 27-year-old male with recent symptoms of fever, chills, and oral ulcers, positive IgM, normal Thyroid-Stimulating Hormone (TSH), negative malaria, Toxoplasma (Tengo), and Vidal tests, normal urine analysis, and normal Hemoglobin A1c (HB1C), with blood pressure readings ranging from 130/90 to 160/90?

Likely Diagnosis: Dengue Fever with Hypertensive Response

The most likely diagnosis is dengue fever presenting with oral ulcers (mucosal involvement), fever, chills, and intermittent hypertensive episodes, supported by positive IgM serology in a young patient with negative malaria, toxoplasma, and typhoid testing.

Clinical Reasoning and Diagnostic Approach

Why Dengue is the Primary Diagnosis

• Positive IgM serology strongly suggests acute dengue infection, though false-positives can occur with other flavivirus exposures 1
• Oral ulcers ("soldiers in mouth") represent mucosal bleeding manifestations, a warning sign of dengue progression 1
• Fever with chills occurring 4-8 days after potential mosquito exposure fits the classic dengue presentation 1
• Thrombocytopenia assessment is critical - if present (<150,000/mL), this significantly increases dengue probability with a positive likelihood ratio of 5.6-11.0 2
• Normal renal function and imaging help exclude other causes of hypertension 1

Hypertension Mechanism in Dengue Context

The intermittent BP spikes (160/90 mmHg) with baseline readings of 130/90 mmHg represent a hypertensive urgency pattern rather than true hypertensive emergency, as there is no evidence of acute end-organ damage 2.

Key pathophysiologic considerations:

• Dengue causes marked activation of the renin-angiotensin system and microvascular damage, which can transiently elevate blood pressure 3, 4
• Inflammatory cytokine release during acute dengue infection affects vascular tone and can cause BP fluctuations 3
• At 27 years old without prior hypertension history, these BP readings likely represent a reactive hypertensive response to acute illness rather than essential hypertension 2

Immediate Management Protocol

Confirm Dengue Diagnosis

• Order dengue PCR/NAAT on serum immediately if symptoms are ≤7 days duration 1
• Repeat IgM testing with confirmatory plaque reduction neutralization test (PRNT) to exclude false-positive results from cross-reactivity with other flaviviruses 1
• Obtain complete blood count with platelet count - thrombocytopenia <150,000/mL has the highest likelihood ratio for malaria diagnosis but is also present in 70-79% of dengue cases 2, 1
• Check hematocrit levels - rising hematocrit (>20% increase from baseline) indicates plasma leakage and requires hospitalization 1
• Measure liver enzymes (AST, ALT), bilirubin, and lactate dehydrogenase to assess for hepatic involvement 2

Blood Pressure Management Strategy

Do NOT treat the blood pressure aggressively in this acute setting 2. Here's why:

• BP readings of 130-160/90 mmHg without symptoms of end-organ damage (no headache, visual changes, chest pain, or neurologic symptoms) do not constitute a hypertensive emergency 2
• Hypertensive urgencies should be managed with oral agents over hours to days, not immediate IV therapy 2
• The BP elevation is likely secondary to the acute dengue infection and inflammatory state 3, 4
• Aggressive BP lowering could precipitate hypotension if the patient progresses to dengue shock syndrome 1

Specific BP monitoring approach:

• Monitor BP every 4-6 hours to detect trends toward hypotension (warning sign of shock) 1
• Target gradual reduction over several hours with mean arterial pressure (MAP) reduction of 20-25% if BP remains >180/110 mmHg 2
• Avoid NSAIDs completely due to bleeding risk in dengue 1
• Consider oral ACE inhibitor or calcium channel blocker only if BP persistently >160/100 mmHg after 24 hours 2

Dengue-Specific Treatment

Fluid management is the cornerstone:

• Ensure oral hydration >2500 mL daily with oral rehydration solutions for patients without shock 1
• Monitor for warning signs requiring hospitalization: persistent vomiting, abdominal pain, mucosal bleeding (already present with oral ulcers), rising hematocrit with falling platelets 1
• Acetaminophen at standard doses for fever and pain - never aspirin or NSAIDs 1

Hospitalization criteria in this patient:

• Oral ulcers represent mucosal bleeding - a warning sign requiring close monitoring 1
• Intermittent hypertension with baseline 130/90 suggests hemodynamic instability 1
• Daily CBC monitoring is essential to track platelet counts and hematocrit 1
• Patient should be hospitalized if platelets <100,000/mL, hematocrit rising >20%, or any signs of plasma leakage 1

Critical Pitfalls to Avoid

Do Not Misinterpret the IgM Result

• IgM false-positives occur frequently with cross-reactivity to other flaviviruses (yellow fever, Japanese encephalitis, Zika) 1, 5
• IgM can persist for months after acute infection, so positive IgM alone does not confirm acute dengue 1
• Confirmatory PRNT testing is essential if clinical picture doesn't fit or if patient has prior flavivirus vaccination 1

Do Not Treat Hypertension as Primary Problem

• This is NOT essential hypertension requiring chronic therapy 2
• The BP elevation is likely reactive to acute dengue infection and inflammatory state 3, 4
• Starting chronic antihypertensive therapy during acute illness is premature and potentially harmful 2
• Reassess BP after dengue resolves (48 hours afebrile without antipyretics) before considering chronic therapy 1

Do Not Prescribe Antibiotics Empirically

• Bacterial co-infection occurs in <10% of viral illnesses including dengue 1
• Empiric antibiotics like azithromycin provide no benefit and contribute to antimicrobial resistance 1
• Only consider antibiotics if blood cultures are obtained and patient develops septic shock or new focal infection 1

Do Not Delay Fluid Resuscitation if Shock Develops

• If BP drops to <90 systolic or pulse pressure <20 mmHg, immediately administer 20 mL/kg isotonic crystalloid bolus over 5-10 minutes 1
• Reassess immediately after bolus and consider colloid solutions for severe shock 1
• Transfer to ICU if hypotension persists despite fluid resuscitation 1

Disposition and Follow-Up

Discharge criteria (if hospitalized):

• Afebrile ≥48 hours without antipyretics 1
• Stable hemodynamic parameters for ≥24 hours without support 1
• Platelet count stable or rising 1
• Adequate oral intake and urine output >0.5 mL/kg/hour 1

Post-discharge instructions:

• Monitor temperature twice daily and return if fever recurs or any warning signs develop 1
• Recheck BP in 2-4 weeks after complete recovery to determine if hypertension persists 2
• If BP remains >130/80 mmHg on two separate occasions after dengue resolution, initiate workup for essential hypertension with fasting glucose, lipids, creatinine, urinalysis, and ECG 2