What genetic mutation defines Sickle Cell Disease (SCD)?
Point mutation in the β-globin gene causing substitution of valine for glutamic acid at position 6 → Hemoglobin S (HbS)
Mnemonic: “Valine Switch = Vaso-occlusion.”
What is the inheritance pattern of Sickle Cell Disease?
Autosomal recessive — disease in HbSS homozygotes, trait in HbAS heterozygotes
Mnemonic: “Two S’s = Sickled, one S = Safe.”
Under what conditions does HbS polymerize and cause sickling?
Low oxygen, acidosis, dehydration, or infection
Mnemonic: “Sickle under Stress.”
What is the average RBC lifespan in Sickle Cell Disease?
10–20 days (due to chronic hemolysis)
Mnemonic: “Sickled = Short-lived.”
What are the main triggers for vaso-occlusive crises in SCD?
- Hypoxia
- Infection
- Dehydration
- Acidosis
- Cold exposure
- Physical/emotional stress
- Pregnancy
Mnemonic: “Sickling Triggers: H.I.D.E. C.P.”
What is usually the first clinical sign of SCD in infants?
Dactylitis (hand-foot syndrome)
Mnemonic: “Dactylitis = Disease debut.”
What causes functional asplenia in SCD?
Splenic infarction from repeated vaso-occlusion → autosplenectomy
Mnemonic: “Spleen Self-destructs.”
What is the most common presentation of Sickle Cell Disease?
Vaso-occlusive (pain) crisis — recurrent severe bone, chest, or abdominal pain
Mnemonic: “Sickle = Sick pain.”
What specific RBC findings are seen on peripheral smear in SCD?
- Sickle-shaped cells
- Target cells
- Howell-Jolly bodies
Mnemonic: “Sickle Targets Howell-Jolly.”
What is the diagnostic test for Sickle Cell Disease?
Hemoglobin electrophoresis showing HbS >90% in disease, 35–45% in trait
Mnemonic: “Electrophoresis = Exposes Sickle.”
What is the screening test for newborns in the U.S.?
Hemoglobin electrophoresis or HPLC
Mnemonic: “HPLC = High Precision Lab Check.”
What imaging test evaluates acute chest syndrome in SCD?
Chest X-ray — new pulmonary infiltrate
Mnemonic: “Chest X-ray = Crisis Check.”
Which brain imaging evaluates silent infarcts or stroke risk in SCD?
MRI/MRA of the brain
Mnemonic: “MRI = Mind Risk Indicator.”
What lab findings confirm hemolysis in SCD?
- ↑ Reticulocytes
- ↑ LDH
- ↑ Indirect bilirubin
- ↓ Haptoglobin
Mnemonic: “Hemolysis = High 3, Low 1.”
What infectious organisms are SCD patients most susceptible to?
- S. pneumoniae
- Salmonella
- H. influenzae
Mnemonic: “Sickles Can’t Stop Shells.”
What is the defining immunologic characteristic of SLE?
Autoantibodies against nuclear and cytoplasmic components forming immune complexes
Mnemonic: “Self-Attack on the Nucleus.”
What hematologic abnormality can SLE cause due to immune destruction and marrow suppression?
Pancytopenia
Mnemonic: “SLE = Suppresses, Lyses Everything.”
What is the key entry requirement for the 2019 ACR/EULAR SLE classification?
Positive ANA titer ≥1:80 (HEp-2 immunofluorescence or equivalent)
Mnemonic: “ANA Always first.”
Can SLE be classified without ANA positivity?
No — if ANA is negative, classification cannot proceed
Mnemonic: “No ANA = No Admission.”
How many total points are required to classify a patient as SLE?
≥10 points (with ≥1 clinical domain)
Mnemonic: “10 points to Lupus.”
What domains are considered in SLE scoring?
10 total (7 clinical, 3 immunologic)
Mnemonic: “7+3 = Systemic SLE.”
What test confirms the presence of SLE-specific antibodies?
Anti-dsDNA or Anti-Smith (6 points each)
Mnemonic: “Double DNA = Definite Lupus.”
What does renal or CNS involvement signify in the SLE scoring system?
High diagnostic weight (most specific for SLE)
Mnemonic: “Brain & Kidney tip the scale.”
