Clinical meaning
Sickle cell disease pathophysiology extends beyond simple vaso-occlusion to encompass sterile inflammation, chronic hemolysis-mediated vasculopathy, and progressive end-organ damage. Free hemoglobin released during intravascular hemolysis scavenges nitric oxide (NO) and generates reactive oxygen species, causing endothelial dysfunction, increased adhesion molecule expression, platelet activation, and a chronic hypercoagulable state. This NO depletion contributes to pulmonary hypertension (present in ~30% of adults with SCD), leg ulcers, priapism, and cerebrovascular disease. Disease-modifying therapies target multiple pathways: hydroxyurea increases HbF, L-glutamine reduces oxidative stress, crizanlizumab blocks P-selectin-mediated adhesion, and voxelotor increases HbS oxygen affinity. The clinician must diagnose genotype-specific complications, prescribe and monitor disease-modifying agents, manage chronic organ damage, coordinate genetic counseling, and direct acute crisis management including exchange transfusion decisions.
Diagnosis & workup
Diagnostics & workup: - Order hemoglobin electrophoresis to confirm genotype: HbSS, HbSC, HbS-beta-thal0/+ - Monitor baseline labs: CBC, reticulocyte count, LDH, indirect bilirubin, haptoglobin, ferritin (if transfused) - Order HbF percentage to guide disease-modifying therapy response (target >20% on hydroxyurea) - Order echocardiogram with tricuspid regurgitant jet velocity (TRV) for pulmonary hypertension screening (TRV ≥2.5 m/s = elevated risk) - Order transcranial Doppler in children ages 2-16 annually for stroke risk (abnormal: velocity ≥200 cm/s = chronic transfusion program) - Order iron studies and liver iron concentration (MRI-based) for transfusion-related iron overload - Order renal function panel and urine albumin-to-creatinine ratio for sickle nephropathy screening - Order pulmonary function tests if chronic respiratory symptoms present