• Content
  • Collaboration
  • About Us
  • Contact Us

SEARCH RESULTS FOR: sickle

central-retinal-artery-occlusion-pathogenesis-and-clinical-findings

Central Retinal Artery Occlusion: Pathogenesis and clinical findings 
Inflammatory Disease: Cardiogenic Embolism: Hypercoagulable state: Hematologic Disease: (i.e. GCA, SLE, GPA) (i.e. Valvular, arrhythmias, congenital defects) (i.e. OCP, Protein C&S deficiency, ATIII deficiency) (i.e. leukemia/lymphoma, sickle cell, polycythemia) Endothelial cell damage Abnormal blood flow 1` coagulation and/or 1 blood viscosity and creates hypercoagulable state causing localized stasis 4, anti-coagulation inflammation 
Abbreviations: • GCA — Giant Cell Arteritis • SLE — Systemic Lupus Erythematosus • GPA — granulomatosis with polyangitis • OCP — Oral contraceptive pill • ATIII — Anti-thrombin Ill 
Thrombus formation 
Blockage of central retinal artery 
Central Retinal Artery Occlusion (CRAO) 
Authors: Graeme Prosperi-Porta Reviewers: Stephanie Cote Usama Malik Johnathan Wong* * MD at time of publication Carotid Artery Atherosclerosis 
Atherosclerotic plaque dislodges from carotid artery 
The retina becomes pale 4, perfusion of retinal Slow retinal artery blood Acute retinal edema Ganglion cells and axons from NI, perfusion arterioles due to upstream flow allows for caused by ischemia results death due to ischemia CRAO segmentation of the blood column in a blurred appearance of the retina results in disc pallor seen months after CRAO The choroidal vessels supplying the macula via the posterior ciliary artery become more prominent within a background of retinal pallor

Acute Chest Syndrome (Sickle Cell Disease)

Hemolytic Anemia - Pathophysiology

Hemolytic Anemia: Pathophysiology behind the Normocytic Anemia
Note
• Extreme bone marrow compensation for hemolysis (↑ RBC synthesis/reticulocytosis) may result in slightly macrocytic anemia (because reticulocytes have larger volumes than RBCs)
    Defects in the RBC’s environment
Defects in RBC membranes
Ex. Hereditary Spherocytosis:
mutation causing deficiency of RBC structural proteins like ankyrin or spectrin
RBC membranes become weakened and form blebs that break off
↓ RBC surface area while volume remains constantà RBC becomes spherical
Spherocytes in spleen trapped and phagocytosed by splenic macrophages (extravascular hemolysis)
Defects in RBC internal contents (thalassemia, hemoglobinopathies, and metabolic defects)
Ex. Sickle Cell Disease: point mutation in hemoglobin (Hgb) structure (GluàVal)
Inappropriate Hgb polymerization in low oxygen environments due to mutationàRBC becomes rigid, forms a sickle shape
Inflexible RBCs become trapped in the spleen’s sinusoid membranes àphagocytosed by splenic macrophages (extravascular hemolysis)
    Infection triggers immune system activation
Autoimmune processes
TTP/HUS (abnormal platelet aggregation blocking blood vessels)
    Production of abnormal
antibodies and immune complexes targeted against RBC surface antigens
Immunoglobulin-bound RBCs are marked for
destruction by the immune system (by either the cell- mediated or complement- mediated pathways)
DIC (fibrin deposition blocking blood vessels)
Artificial heart valve
                RBCs are sheared when they flow past an abnormal surface
     Rate of hemolytic RBC destruction > rate of bone marrow RBC synthesis (reticulocytosis)
↓ total number of RBCs in the body (despite normal RBC production/volume)
Normocytic anemia
Authors: Yan Yu Katie Lin Man-Chiu Poon* Reviewers: Andrew Brack Julia Heighton JoyAnne Krupa Lynn Savoie* * MD at time of publication
     Legend:
 Pathophysiology
 Mechanism
Sign/Symptom/Lab Finding
  Complications
Re-Published June 15, 2019 on www.thecalgaryguide.com

Priapism

Priapism: Pathogenesis
   Post-cavernosal venous occlusion
↑ nitric oxide from cavernous nerve plexus and cavernosal sinus endothelia
Impaired detumescence (erection-ending) pathways
Post-cavernosal venous drainage is mechanically obstructed e.g. sickle cell disease, dialysis etc.
Ischemic (Low-flow):
Inadequate venous function
Blood pools in corpora cavernosa
Cavernosal cell metabolism uses O2 and releases CO2 into pooled blood
     Trabecular smooth muscle relaxes
Cavernosal artery smooth muscle relaxes
Lack of norepinephrine action on penile SM
Post-cavernosal venules are compressed against tunica albuginea
Trabecular smooth muscle and cavernosal artery smooth muscle do not contract
↑ pressure in corpora
                 ↑PCO2 ↓pH
Acidosis
↓PO2
Tissue hypoxia
Tissue damage
Irreversible fibrosis leading to erectile dysfunction
Priapism
Prolonged erection lasting more than 4 hours; in absence of sexual stimulation; not relieved by ejaculation
                     Trauma to penis or adjacent areas
Authors:
Arsalan Ahmad
Reviewers:
Alec Mitchell
Darren Desantis*
Yan Yu*
* MD at time of publication
Cavernosal artery is damaged
Excessive, unregulated arterial blood flow into corpora cavernosa
Pain
Non-ischemic (High-flow):
    Uncontrolled arterial flow
↑ volume of blood in corpora
↑ pressure in corpora
      Legend:
 Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
  Complications
 Published September 22, 2019 on www.thecalgaryguide.com

急性胸部综合征镰状细胞贫血发病机制和临床表现

急性胸部综合征(镰状细胞贫血):发病机制和临床表现

Sickle Cell Disease Pathogenesis Clinical Findings and Complications

Sickle Cell Disease: Pathogenesis, Clinical Findings, and Complications
DNA point mutation in chromosome 11 causes a substitution of glutamate to valine for the sixth amino acid of the β-globin chain
Authors: Yang (Steven) Liu Priyanka Grewal Reviewers: Alexander Arnold Luiza Radu JoyAnne Krupa Yan Yu* Lynn Savoie* * MD at time of publication
  Hemoglobin S (HbS) variant formed instead of normal Hemoglobin A (HbA)
  Hb electrophoresis shows approximately 45% HbS, 52% HbA (ααββ), 2% HbA
Hb electrophoresis shows approximately 90% HbS, 8% HbF, & 2% HbA .
No HbA present
  (ααδδ), & 1% HbF (ααγγ;2 fetal hemoglobin)
Heterozygous: point mutation in one of the two chromosomes (Hb AS)
Sickle cell trait
(asymptomatic unless severely hypoxic)
Homozygous: point mutation in both chromosomes (Hb SS)
Sickle cell disease
An inherited blood disorder characterized by defective hemoglobin that leads to red blood cells sickling
2
      Dehydration Hypoxemia
Acidosis
↓ Volume of RBC cytoplasm
↓ O2 Saturation of Hb
O morereadily 2
released from Hb in low pH environment
↑ Concentration of deoxygenated HbSinred blood cells (RBCs)
Hydrophilic glutamate→ hydrophobic valine substitution makes HbS less soluble in the cytoplasm & more prone to polymerization & precipitation in its deoxygenated state
↑ Concentration of deoxygenated Hb in RBC leads to ↑ polymerization rate Polymerized & precipitated HbS forms long needle-like fibers
        RBC shape becomes sickled
Sickle cells on peripheral blood smear
     Vaso-occlusion
(sickled RBCs lodge in small vessels, blocking bloodflow to organs & tissues)
Blockage of venous outflow
Occlusion of vessels in lungs ↑ pulmonary blood pressure
Fluid extravasates into interstitial tissue leading to pulmonary edema
Acute chest syndrome (chest pain, hypoxemia (↓blood oxygen), etc.)**
to the penis:
to the spleen:
Priapism (persistent, painful erection)
Splenic Sequestration (blood pools in spleenà splenomegaly & hypotension)
Extravascular hemolysis (macrophages in the spleen phagocytose sickled RBCs)
Normocytic anemia
↑Marrow erythropoiesis (RBC production) to compensate for hemolysis
                  Infarction of bone
Pain crises
If occurring in hands
Dactylitis (inflammation of digits)
Blockage of arteries ↓ oxygenation of organs & tissues
Vaso-occlusion of the splenic artery
Splenic infarction (↓ blood supply leads to tissue death)
RBC inclusions (structures found in RBCs) not removed by spleen
Howell-Jolly bodies (RBC DNA remnants) on blood smear
Vaso-occlusion of other arteries (cranial, renal, etc)
Stroke, renal failure
↑ RBC breakdown
↑ Unconjugated bilirubin released from RBC breakdown
RBC precursors (reticulocytes) are released into the blood stream
Reticulocytosis (increased number of immature red blood cells) on peripheral blood smear
Patient’s RBC level becomes dependent on increased marrow activity
Bone marrow infarction or viral infections (i.e. Parvovirus B19) suppresses bone marrow activity
Aplastic crises (profound anemia)
       ** See corresponding Calgary Guide slide(s)
↑ Serum level of unconjugated bilirubin
Some of the circulating unconjugated bilirubin deposits in the skin
Jaundice (yellowing of skin)
↑ Conjugation of bilirubin in liver
↑Amounts of conjugated bilirubin released into bile
Gallstone formation
Cholelithiasis (presence of gallstones in the gallbladder)
         Spleen releases invasive encapsulated bacteria (eg. Haemophilus influenzae, Streptococcus pneumoniae, Neisseria meningitidis) into circulation, which causes infections
         Meningitis
Sepsis
  Legend:
 Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
 Complications
 Published Sept 16, 2013, updated Apr 29, 2024 on www.thecalgaryguide.com

© 2025 - The Calgary Guide to Understanding Disease

Disclaimer