A 28-year-old Indian woman with sickle cell disease presents with acute chest pain, fever, and pulmonary infiltrates. Which finding best distinguishes acute chest syndrome from simple vaso-occlusive pain crisis?

Question

Accepted Answer

C. Presence of new pulmonary infiltrates on chest X-ray. ## Acute Chest Syndrome vs. Vaso-Occlusive Pain Crisis

### Definition and Pathophysiology

**Key Point:** Acute chest syndrome (ACS) is defined by the presence of **new pulmonary infiltrates** on imaging (chest X-ray or CT) in a patient with sickle cell disease presenting with respiratory symptoms, fever, or chest pain. This is the cardinal discriminating feature.

### Comparison Table

| Feature | Vaso-Occlusive Crisis (VOC) | Acute Chest Syndrome (ACS) |
| --- | --- | --- |
| **Primary pathology** | Bone/soft tissue infarction | Pulmonary infarction/infection |
| **Chest imaging** | Normal or old changes | **New infiltrates** (lobar or segmental) |
| **Fever** | May be present | Usually present |
| **Respiratory symptoms** | Absent or mild | Dyspnea, cough, hypoxemia |
| **Mortality** | Low | 1–5% (second leading cause of death in SCD) |
| **Triggers** | Dehydration, cold, stress | Infection (bacterial, viral, atypical), fat embolism, RBC sickling in lungs |
| **Management** | Hydration, analgesia, O~2~ | Antibiotics, transfusion, O~2~, supportive care |

### Why New Pulmonary Infiltrates Are Diagnostic

**High-Yield:** ACS is a medical emergency in sickle cell disease. The diagnosis REQUIRES both clinical features (fever, chest pain, dyspnea) AND radiologic evidence of new pulmonary infiltrates. Without infiltrates, it is classified as uncomplicated VOC.

**Clinical Pearl:** ACS can progress rapidly to acute respiratory distress syndrome (ARDS) and multi-organ failure. Early recognition via chest imaging and aggressive management (exchange transfusion, antibiotics) are lifesaving.

### Why Other Options Are Non-Specific

Elevated reticulocyte count, LDH, and indirect bilirubin reflect chronic hemolysis in all patients with sickle cell disease and are present in both VOC and ACS. Sickling on blood smear is also non-specific. Only the **presence of new pulmonary infiltrates** distinguishes ACS from simple VOC.

Answer

A. Elevated LDH and indirect bilirubin

Answer

B. Elevated reticulocyte count

Answer

D. Sickling of RBCs on blood smear

A 28-year-old Indian woman with sickle cell disease presents with acute chest pain, fever, and pulmonary infiltrates. Which finding best distinguishes acute chest syndrome from simple vaso-occlusive pain crisis?

Explanation

Acute Chest Syndrome vs. Vaso-Occlusive Pain Crisis

Definition and Pathophysiology

Comparison Table

Why New Pulmonary Infiltrates Are Diagnostic

Why Other Options Are Non-Specific

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Feature	Vaso-Occlusive Crisis (VOC)	Acute Chest Syndrome (ACS)
Primary pathology	Bone/soft tissue infarction	Pulmonary infarction/infection
Chest imaging	Normal or old changes	New infiltrates (lobar or segmental)
Fever	May be present	Usually present
Respiratory symptoms	Absent or mild	Dyspnea, cough, hypoxemia
Mortality	Low	1–5% (second leading cause of death in SCD)
Triggers	Dehydration, cold, stress	Infection (bacterial, viral, atypical), fat embolism, RBC sickling in lungs
Management	Hydration, analgesia, O₂	Antibiotics, transfusion, O₂, supportive care