After reading this note you will be able to describe the clinical approach to a patient with sickle cell disease, recognise key examination findings, interpret the essential investigations and outline immediate and definitive management – remembering to verify doses and local protocols against the Kenya Ministry of Health guidelines and your hospital formulary.
Definition
A hereditary hemoglobinopathy caused by a point mutation in the β‑globin gene (HBB) that produces haemoglobin S (HbS). When deoxygenated, HbS polymerises, distorting red cells into a sickle shape, leading to chronic haemolysis and vaso‑occlusion.
Anatomy and physiology you need
| Structure | Relevance to disease |
|---|---|
| Red blood cell membrane | Polymerised HbS stiffens membrane → reduced deformability |
| Microvasculature (arterioles, capillaries) | Narrow lumen predisposes to sickling‑induced blockage |
| Spleen | Repeated infarction → functional asplenia, susceptibility to encapsulated organisms |
| Bone marrow | Hyperplasia from chronic anaemia → marrow expansion, pain |
| Liver & biliary system | Haemolysis → bilirubin overload, gallstones |
| Kidney medulla | Hyperosmolar, low pH environment promotes sickling → papillary necrosis |
Causes and risk factors
| Factor | Why it matters in Kenya |
|---|---|
| Homozygous HbSS genotype | Most severe phenotype, common in certain ethnic groups |
| Heterozygous HbAS (trait) + other haemoglobinopathies (e.g., HbC) | Can modify severity when co‑inherited |
| Co‑infection with malaria | Parasite‑induced haemolysis worsens anaemia; sickle cells confer some protection, altering prevalence |
| HIV infection | Immunosuppression increases infection risk; drug interactions with hydroxyurea |
| Tuberculosis | Chronic inflammation and marrow suppression exacerbate anaemia |
| Recurrent bacterial infections (especially encapsulated) | Functional asplenia predisposes to sepsis |
| Nutritional deficiencies (vit B12, folate) | Impair erythropoiesis, aggravate anaemia |
| Dehydration, hypoxia, cold exposure | Promote sickling crises |
Pathophysiology
Genetic mutation → HbS production → ↓ oxygen affinity → HbS polymerisation → RBC sickling → ↑ rigidity & adhesion → vaso‑occlusion → tissue ischaemia & pain → chronic haemolysis → anaemia, jaundice, gallstones → organ damage (splenic infarction → functional asplenia, renal papillary necrosis, pulmonary hypertension).
Arrows format:
Mutation → HbS → Polymerisation → Sickling → Occlusion → Ischaemia → Pain + Hemolysis → Anaemia → End‑organ complications.
Clinical features
| History domain | Key questions | Why it matters |
|---|---|---|
| Pain | Onset, location, duration, triggers, pattern (vaso‑occlusive crisis vs. chronic), response to analgesia | Pain is the hallmark of sickle cell disease (SCD). Vaso‑occlusive crises produce acute, severe, often migratory pain; chronic pain may indicate avascular necrosis or neuropathic component. |
| Fever / infection | Recent fever, cough, dysuria, wound infection, sick contacts, HIV/TB status, malaria exposure | SCD patients have functional asplenia; infections (especially encapsulated bacteria, malaria, TB, HIV) precipitate crises and can be life‑threatening. |
| Anemia symptoms | Fatigue, dyspnoea on exertion, palpitations, dizziness, jaundice | Chronic hemolysis leads to anemia; worsening may signal aplastic crisis, splenic sequestration, or hemolytic flare. |
| Growth & development | Height/weight trends, school performance, puberty timing | Chronic disease and repeated crises can impair growth and delay puberty. |
| Past crises | Number, severity, triggers, need for hospitalization, transfusions | Frequency of crises guides severity classification and prophylactic strategies. |
| Transfusion history | Number of units, allo‑immunisation, iron overload symptoms | Repeated transfusions increase risk of allo‑antibodies and iron overload; influences future management. |
| Family history | Sickle trait/disease in relatives, consanguinity | Autosomal recessive inheritance; carrier status in parents informs counselling. |
| Vaccination & prophylaxis | Penicillin prophylaxis, pneumococcal, meningococcal, Hib vaccines, folic acid use | Prevents overwhelming infections; adherence reflects risk mitigation. |
| Co‑morbidities | HIV status, TB treatment, malaria prophylaxis, rheumatic fever history | Co‑existing infections/tropical diseases exacerbate hemolysis and vaso‑occlusion. |
| Social factors | Access to clean water, nutrition, distance to health facility | Determines ability to seek timely care during crises. |
Examination findings and pathophysiologic basis
| Finding | Explanation |
|---|---|
| Pallor | Reduced hemoglobin from chronic hemolysis. |
| Jaundice (scleral, skin) | Accumulation of unconjugated bilirubin due to increased red cell breakdown. |
| Splenomegaly (early childhood) → autosplenectomy (adolescence) | Repeated splenic infarction leads to progressive fibrosis and loss of function; early enlargement reflects sequestration episodes. |
| Hepatomegaly | Congestion from sickling in hepatic sinusoids; iron overload from transfusions. |
| Bone tenderness / swelling | Vaso‑occlusion in marrow causing infarction; may progress to osteomyelitis (especially Salmonella). |
| Joint limitation | Avascular necrosis of femoral/shoulder heads from repeated infarcts. |
| Growth retardation | Chronic anemia and metabolic demand impair linear growth. |
| Cardiac murmur (flow murmur) | High‑output state secondary to anemia. |
| Peripheral edema | Renal concentrating defect or right‑heart strain from chronic anemia. |
| Neurological deficits | Stroke from large‑vessel occlusion; silent infarcts present as subtle neurocognitive changes. |
| Chest findings (crepitations, tachypnoea) | Acute chest syndrome – pulmonary vaso‑occlusion, infection, or fat embolism. |
Differential diagnosis
| Condition | Points toward it | Distinguishing feature |
|---|---|---|
| Acute vaso‑occlusive crisis (SCD) | Known SCD, severe episodic pain, triggers (cold, dehydration) | Pain pattern, sickle cells on smear, normal WBC unless infection |
| Septicemia (encapsulated bacteria) | Fever, chills, leukocytosis, asplenia | Positive blood cultures, rapid deterioration, no sickle cells needed |
| Malaria | Recent travel, fever spikes, anemia, thrombocytopenia | Plasmodium parasites on thick smear, rapid response to antimalarials |
| Aplastic crisis (Parvovirus B19) | Sudden drop in Hb, low retic count, mild/no pain | Very low retic, PCR for Parvovirus, absence of sickle cells in smear |
| Splenic sequestration | Rapid splenomegaly, acute anemia, reticulocytosis | Enlarged spleen on exam, ultrasound shows pooling |
| Acute chest syndrome | Chest pain, cough, hypoxia, new infiltrate | CXR infiltrates, hypoxia, may coexist with vaso‑occlusive pain |
| Osteomyelitis (Salmonella) | Localized bone pain, fever, elevated ESR/CRP | Positive bone culture, MRI shows sequestrum |
| Thalassemia major | Microcytic anemia, skeletal deformities, family history | Target cells on smear, absent HbS on electrophoresis |
| Rheumatic fever | Migratory arthritis, carditis, recent strep infection | Jones criteria, elevated ASO titre, no sickle cells |
Investigations
| Test | What it answers | Interpretation |
|---|---|---|
| Complete blood count | Anemia severity, leukocytosis, platelet count | Hb low, MCV normocytic, retic high (hemolysis) or low (aplastic) |
| Peripheral smear | Presence of sickled erythrocytes, target cells, Howell‑Jolly bodies | Sickled cells confirm SCD; Howell‑Jolly → functional asplenia |
| Hemoglobin electrophoresis / HPLC | Hb genotype, proportion of HbS, HbF, HbA | HbSS >90% HbS, HbSC shows HbS + HbC, HbF level predicts severity |
| Reticulocyte count | Bone‑marrow response to anemia | Elevated in hemolysis, suppressed in aplastic crisis |
| Serum bilirubin (direct/indirect) | Hemolysis vs. hepatic obstruction | Predominantly indirect bilirubin in hemolysis |
| Liver function tests | Hepatopathy, iron overload | Elevated transaminases may indicate sickle‑cell hepatopathy |
| Renal function (creatinine, eGFR, urinalysis) | Renal tubular dysfunction, proteinuria | Low concentrating ability, micro‑albuminuria signals early nephropathy |
| Chest X‑ray | Acute chest syndrome, pneumonia | New infiltrate, pleural effusion |
| Ultrasound abdomen | Splenic size (sequestration), hepatic congestion | Enlarged spleen in sequestration; shrunken in autosplenectomy |
| Blood cultures | Bacterial sepsis | Positive growth guides antibiotics |
| Malaria rapid test / thick smear | Malaria infection | Positive parasites confirm malaria |
| HIV test | Co‑infection status | Positive → need integrated care |
| Iron studies (serum ferritin, transferrin saturation) | Iron overload from transfusions | Ferritin markedly raised, saturation >50% |
Diagnosis and severity
Diagnostic criteria (clinical + laboratory):
- Clinical picture consistent with hemolytic anemia, vaso‑occlusive pain, or related complications.
- Laboratory confirmation of sickle hemoglobin (HbS) ≥ 50 % on electrophoresis/HPLC, or presence of sickled cells on smear with compatible family history.
Severity classification (adapted for Kenyan setting)
| Category | Clinical parameters | Management implications |
|---|---|---|
| Mild | ≤2 pain crises/year, no hospitalisation for ACS, normal growth, Hb ≥ 8 g/dL, no organ damage | Routine prophylaxis, folic acid, vaccination, education; outpatient follow‑up. |
| Moderate | 3–5 crises/year or ≥1 ACS episode, Hb 7–8 g/dL, mild splenomegaly or early organ changes, growth <5th percentile | Consider chronic transfusion programme, hydroxyurea initiation, regular monitoring of organ function. |
| Severe | ≥6 crises/year or ≥2 ACS, Hb < 7 g/dL, documented stroke, avascular necrosis, renal/hepatic dysfunction, iron overload | Aggressive disease‑modifying therapy (hydroxyurea, chronic transfusion, possible bone‑marrow transplant referral), multidisciplinary care, close cardiac/renal surveillance. |
Severity guides intensity of disease‑modifying therapy, frequency of specialist review, and need for psychosocial support. Regular reassessment (at least annually) is essential, as disease trajectory can change with age, infection exposure, and treatment adherence.
Management
Immediate stabilisation
| Situation | Action | Rationale |
|---|---|---|
| Acute vaso‑occlusive pain crisis | Give rapid‑acting opioid (e.g. morphine) + IV fluids (isotonic) | Relieve pain, improve microvascular flow, prevent dehydration‑induced sickling |
| Acute chest syndrome (ACS) | Admit to high‑dependency, give supplemental O₂ to keep SpO₂ > 94 %, start broad‑spectrum antibiotics, consider blood transfusion | Prevent respiratory failure; infection and sickling both contribute |
| Severe anaemia (Hb < 5 g/dL) or hemodynamic compromise | Urgent packed red cell transfusion (simple or exchange) | Improves oxygen‑carrying capacity, reduces sickled cells |
| Stroke or neurologic deficit | Immediate exchange transfusion, start antiplatelet (aspirin) after imaging | Reduces Hb S proportion, limits infarct extension |
| Fever > 38.5 °C in a child | Full septic work‑up, start empiric IV antibiotics (e.g. ceftriaxone) | Children with SCD are functionally asplenic |
Definitive treatment
- Hydroxyurea (myelosuppressive agent) – increases fetal haemoglobin, lowers VOC frequency, reduces transfusion need. Start after baseline blood counts, monitor CBC every 4 weeks.
- Chronic transfusion programme – for recurrent ACS, stroke prevention, or severe anaemia; aim to keep Hb S < 30 %. Use simple or exchange transfusion depending on iron load.
- Penicillin prophylaxis (until age 5) – prevents pneumococcal sepsis; give oral penicillin V.
- Vaccinations – pneumococcal (PCV13 + PPSV23), Haemophilus influenzae type b, meningococcal, influenza annually.
- Folic acid supplementation – supports erythropoiesis; give oral folic acid daily.
- Education & psychosocial support – sickle‑cell crisis plan, avoidance of extreme temperatures, hydration, prompt medical review for fever or pain.
Monitoring & follow‑up
- Clinic review every 3–6 months (CBC, reticulocyte count, renal & liver function, urine albumin).
- Annual transcranial Doppler (TCD) in children 2–16 y to screen for stroke risk.
- Iron studies if on chronic transfusion; start chelation if ferritin rises markedly.
- Assess growth, puberty, neuro‑cognitive development in paediatrics.
Contra‑indications & safety
- Hydroxyurea: avoid in pregnancy, severe renal/hepatic impairment, active infection with neutropenia.
- Blood transfusion: screen for allo‑antibodies; avoid in patients with severe hypervolaemia unless exchange is used.
- NSAIDs: use cautiously in renal dysfunction or active peptic ulcer disease.
Complications and prognosis
| Complication | Typical presentation | Key preventive / therapeutic measure |
|---|---|---|
| Acute chest syndrome | New infiltrate + fever + chest pain or dyspnoea | Early antibiotics, O₂, transfusion, incentive spirometry |
| Stroke (ischemic) | Focal neuro deficit, seizures | TCD screening, chronic transfusion, aspirin |
| Splenic sequestration | Rapid abdominal distension, falling Hb, thrombocytopenia | Immediate transfusion, splenectomy if recurrent |
| Aplastic crisis (parvovirus B19) | Sudden severe anaemia, low retic count | Supportive care, transfusion; monitor for recovery |
| Chronic kidney disease | Proteinuria, rising creatinine | ACE‑inhibitor/ARB, control hypertension, avoid nephrotoxins |
| Leg ulcers | Chronic painful ulcer on lower leg | Wound care, compression, optimise haemoglobin |
| Gallstones (pigment) | RUQ pain, jaundice | Ultrasound screening, cholecystectomy if symptomatic |
| Priapism (male) | Persistent painful erection > 4 h | Ice packs, analgesia, aspiration ± phenylephrine; urology referral |
| Iron overload (from transfusion) | Elevated ferritin, organ dysfunction | Iron chelation therapy (deferasirox, deferoxamine) |
Prognosis – With modern preventive care (vaccination, penicillin, hydroxyurea, transfusion programmes) life expectancy in Kenya approaches 50–60 years, but morbidity from organ damage remains high. Early detection of complications and adherence to therapy are the main determinants of outcome.
High‑yield exam points
- Look‑alike conditions: vaso‑occlusive pain vs. osteomyelitis (often Salmonella); ACS vs. bacterial pneumonia; splenic sequestration vs. acute abdomen.
- Commonest wrong first step: giving NSAIDs alone for a VOC without adequate hydration and opioid analgesia.
- Bedside examiner questions:
- “What is the pathophysiological basis for the protective effect of hydroxyurea?”
- “How would you differentiate splenic sequestration from an aplastic crisis?”
- “What is the target Hb S percentage in a chronic transfusion programme and why?”
- “Explain why children with SCD require lifelong pneumococcal vaccination.”
Clinical case
Case: A 7‑year‑old boy presents with a 2‑day history of fever (38.9 °C), cough, and left‑sided chest pain. He is tachypnoeic (28 bpm), SpO₂ 91 % on room air, and has dullness to percussion over the left lower zone. Past history: diagnosed with sickle cell disease (HbSS) at 6 months, on penicillin prophylaxis, no prior transfusions.
Key findings: New infiltrate on chest X‑ray, Hb 7 g/dL, retic count 12 %.
Questions
- What is the most likely diagnosis?
Acute chest syndrome (ACS).
- What is the immediate management priority?
Admit to high‑dependency, start supplemental O₂, give broad‑spectrum IV antibiotics, and arrange urgent simple or exchange transfusion to raise Hb and reduce Hb S.
- Which long‑term intervention will reduce his risk of future ACS episodes?
Initiation of hydroxyurea therapy after baseline blood counts, with regular monitoring.
Practice questions
Question 1
A 3‑year‑old with known HbSS presents with sudden abdominal distension, pallor, and a rapid drop in haemoglobin from 9 g/dL to 5 g/dL. Platelets are 80 × 10⁹/L. What is the next best step?
A. Give oral iron tablets
B. Immediate packed red cell transfusion
C. Start high‑dose vitamin K
D. Observe and repeat CBC in 24 h
Answer: B. Immediate packed red cell transfusion – The picture is splenic sequestration; rapid volume replacement is essential to prevent circulatory collapse.
Question 2
A 15‑year‑old with SCD complains of a painful, swollen left knee for 5 days. He is afebrile, ESR is mildly raised. What distinguishes osteomyelitis from a vaso‑occlusive crisis?
A. Presence of fever
B. Elevated ESR
C. Localised warmth and tenderness over bone, not joint
D. Response to opioids
Answer: C. Localised warmth and tenderness over bone, not joint – Osteomyelitis often involves the metaphysis with focal signs, whereas VOC pain is more diffuse and joint‑sparing.
Question 3
A child with SCD is started on hydroxyurea. Which laboratory parameter must be checked before the first dose and then monitored monthly?
A. Serum creatinine
B. Liver transaminases
C. Complete blood count with differential
D. Serum ferritin
Answer: C. Complete blood count with differential – Baseline neutrophil and platelet counts are required to avoid severe myelosuppression.
Question 4
A 22‑year‑old woman with HbSC disease presents with painless jaundice and right upper quadrant pain. Ultrasound shows multiple gallstones. What is the definitive management?
A. Observation only
B. Oral ursodeoxycholic acid
C. Laparoscopic cholecystectomy
D. Endoscopic sphincterotomy
Answer: C. Laparoscopic cholecystectomy – Symptomatic pigment gallstones in SCD are best treated surgically; endoscopic options are reserved for choledocholithiasis.
Question 5
During a routine visit, a 10‑year‑old with SCD has a normal physical exam but a urine albumin‑creatinine ratio of 35 mg/mmol. What does this indicate?
A. Acute renal failure
B. Early nephropathy – start ACE‑inhibitor
C. Dehydration – increase fluids only
D. Laboratory error – repeat test
Answer: B. Early nephropathy – start ACE‑inhibitor – Micro‑albuminuria signals sickle‑cell nephropathy; ACE‑inhibitors slow progression.
Drafted with AI assistance from standard references and reviewed for structure. Check details against your lecture notes and the Kenya MoH guideline.