​Pathology - Thrombotic Thrombocytopenic Purpura (TTP)
This condition is medically identified by the presence of five specific symptoms: fever, low platelet count, kidney failure, abnormal breakdown of red blood cells with fragmented cells called schistocytes, and abnormalities in the nervous system. The idiopathic form of this thrombotic microangiopathy commonly presents with a deficit of the vWF cleaving protease ADAMTS-13, caused by an autoimmune response. This leads to the presence of excessively large multimers of vWF, which in turn promote excessive platelet aggregation. Thrombocytopenia occurs due to the excessive formation of microvascular thrombi. Petechiae and purpura occur as a consequence of thrombocytopenia. Cerebral microvascular occlusion can result in various neurological symptoms such as headache, seizures, localized neurological impairments, or alterations in mental status. Renal microinfarcts result in the development of acute renal failure, which is characterized by an increase in serum creatinine levels. Erythrocytes undergo shearing when they come into contact with microthrombi, leading to the development of hemolytic anemia. This condition causes the formation of schistocytes and jaundice. Plasma exchange is the preferred treatment and platelet transfusion can actually exacerbate the production of microthrombi.

Pathology - Heparin-Induced Thrombocytopenia (HIT)
Heparin-induced thrombocytopenia (HIT) is a problem that can occur as a result of heparin treatment and can lead to the formation of blood clots in veins or, less commonly, arteries. The pathogenesis of this condition is characterized by the production of an immunological complex that is antigenic, leading to the development of a type II hypersensitivity reaction. Heparin molecules attach to the platelet-specific chemokine platelet factor 4 (PF4) and, as a result, trigger the creation of IgG (HIT antibodies). These antibodies then connect to the heparin-PF4 molecule, creating an immunological complex. The FcγIIa receptor found on platelets in the bloodstream attaches to the heparin-PF4-IgG immunological complex. As a result, macrophages in the spleen eliminate the platelets, leading to thrombocytopenia. Nevertheless, since both the PF4 and IgG components of the complex have the ability to attach to platelets, it is possible for a platelet that is carrying this immunological complex to adhere to another platelet while circulating in the bloodstream.
The process of cross-linking platelets through the immune complex results in more platelet aggregation and activation, which leads to the release of more PF4 capable of binding heparin. This, in turn, causes the creation of a paradoxical thrombus despite the presence of the anticoagulant. Arterial emboli resulting from HIT have become trapped in the microvasculature surrounding the first metatarsal in this patient, causing ischemia. The initial measure in the therapy process involves discontinuing the administration of heparin.

Pathology - Colorectal cancer
The patient exhibits symptoms consistent with anemia, and the test results suggest that the underlying cause is iron deficiency resulting from ongoing blood loss. Lesions affecting the descending colon typically result in obstructive symptoms because to its narrower diameter, but lesions in the ascending colon tend to produce bleeding, which can lead to iron-deficiency anemia. His risk factors consist of his smoking history and a confirmed family history of colon cancer. A well-documented series of genetic mutations takes place in colorectal cancers: APC → K-RAS → DCC → p53. Colon cancer encompasses a range of different kinds, some of which have a hereditary component. Hereditary nonpolyposis colorectal cancer is linked to genetic alterations in mismatch repair. This patient should have additional assessment, specifically a colonoscopy, to gather tissue samples and get a more conclusive diagnosis.

Pathology - ​Gastric adenocarcinoma
 The historical background of peptic ulcer disease suggests a possible infection with H. pylori, a bacterium known to induce gastritis and intestinal metaplasia. If a left supraclavicular node, also known as Virchow's node, is present, it indicates metastasis through lymphatic drainage. Additional observations include of acanthosis nigricans, which is the darkening of the skin, the Leser-Trelat sign, which indicates the presence of a large number of seborrheic keratosis, and the Sister Mary Joseph sign, which suggests metastasis to periumbilical nodes based on the existence of a palpable periumbilical node. It is crucial to emphasize that the diffuse type of gastric adenocarcinoma is not linked to H. pylori infection. This illness has a bleak prognosis, and the treatment may involve a mix of surgical intervention, chemotherapy, and/or radiation therapy. Palliative care is typically initiated soon after diagnosis because this disease is frequently inoperable.

Pathology - Idiopathic (Immune) Thrombocytopenic Purpura
Idiopathic thrombocytopenic purpura (ITP), sometimes called immunological thrombocytopenic purpura, a type II hypersensitivity reaction. This acute onset of the illness most typically occurs in children following a viral upper respiratory tract infection. The pathogenesis relies around the development of IgG antibodies against platelet membrane glycoproteins, notably GpIIb/IIIa receptors. Coating of platelets by IgG leaves them vulnerable to opsonization and phagocytosis by macrophages in the spleen. The lower platelet counts lead to localized cutaneous hemorrhages known as petechiae, described in the vignette, as well as ecchymoses. Other symptoms may include epistaxis, hematuria, or hematochezia. Splenomegaly and lymphadenopathy could be expected in malignant causes of thrombocytopenia. ITP is normally selflimiting in children; nevertheless, severely low levels of platelets (<10,000/mm3) produces risk for serious hemorrhage, bleeding into vital organs, and cerebral hemorrhage. In adults, the problem is most often chronic and is connected with other autoimmune diseases or large array of medications.

Pathology - Hereditary Spherocytosis
Hereditary spherocytosis (HS) resulting in the development of calcium bilirubinate (pigment) gallstones and subsequent choledocholithiasis. HS is an autosomal dominant condition resulting in defective proteins (e.g., ankyrin, band 3.1, spectrin) that interact with the RBC skeleton and plasma membrane. Decreased membrane contact leads to small, spherical RBCs with no central pallor (spherocytes). The membrane defect and defective Na+/K+-ATPase pump results in increased permeability to sodium (positive osmotic fragility test as mentioned in the vignette). Extravascular hemolysis of the aberrant cells results in jaundice, splenomegaly, and high indirect (unconjugated) bilirubin levels. Excess bilirubin in bile contributes to production of calcium bilirubinate (black pigment) gallstones. In this example, gallstones have become lodged in the CBD (choledocholithiasis) generating high direct (conjugated) bilirubin and elevated alkaline phosphatase. As the patient is afebrile with negative Murphy’s sign and absent leukocytosis, cholangitis is not anticipated and elective removal of the gallbladder is advised to prevent recurrence and complications. Vaccination for encapsulated organisms is also indicated in patients with autosplenectomy.

​Pathology - Hemophilia
Hemophilia A is a coagulation problem from deficiency in factor VIII, and consequent hemarthrosis of his knee. PTT is prolonged when the intrinsic pathway is damaged; however, in cases of hemarthrosis, PT may also be prolonged as the extrinsic pathway clotting factors are spent in containing a hemorrhage. Hemophilia A is nearly five times more common than hemophilia B (deficiency of factor IX) and is transmitted in an Xlinked recessive manner, however family history may be lacking as 30% of cases are spontaneous mutations. The illnesses are clinically indistinguishable and need testing of serum plasma components. Hemophilia occurs on a range of severity, based on the relative insufficiency of the clotting factor. Less than one percent (<1%) activity is considered serious and results in spontaneous bleeding. Patients with mild hemophilia (5–40% factor activity) bleed heavily at times of trauma and surgery. Those with 1 to less than 5% activity have moderate bleeding episodes. Intracranial hemorrhage is the most common cause of mortality and is commonly spontaneous in moderate and severe illnesses. A typical consequence is joint destruction from recurrent hemarthrosis. In this scenario, an arthrocentesis of the joint would be therapeutic and diagnostic.

Pathology - von Willebrand Disease
von Willebrand disease (vWD) is the most common inherited bleeding illness. It is autosomal dominant and is most commonly (in vWD Type I) the outcome of a quantitative deficiency in von Willebrand factor (vWF). vWF is a vital component of hemostasis, forming the adhesive bond between platelets and the damaged endothelium, and also serves as a carrier protein for factor VIII. The condition results in prolonged bleeding time on coagulation testing, as faulty platelet adhesion impedes development of the initial platelet plug, and sometimes prolonged PTT, due to its role in factor VIII availability. Abnormal ristocetin cofactor assay or reduced vWF antigen validates the diagnosis.
Patients may initially be recognized via operations such as circumcision, dental work, or surgery. Other manifestations may include easy bruising, excessive bleeding with loss of deciduous teeth or delivery, epistaxis, and menorrhagia. Severe bleeding, such as recurrent hemarthrosis in hemophilia, is unusual. Desmopressin (DDAVP) promotes release of vWF and factor VIII and is a mainstay of therapy, with oral contraceptive pills (estrogen also boosts vWF levels) widely used for menorrhagia.

​Pathology - Disseminated Intravascular Coagulation (DIC)
DIC may occur secondary to gram-negative bacterial septic shock.
DIC is a thrombohemorrhagic illness that develops from activation of the coagulation cascade and consumption of coagulation factors as a complication of a number of disorders. Gram-negative organisms (such as N. meningitidis as in this case or most commonly E. coli), trauma, obstetric complications, malignancy or other causes of vascular damage, and inflammatory mediators result in the release or exposure of tissue factor, the most fibrogenic substance known, initiating coagulation. Fibrin thrombi form in the microcirculation, consuming coagulation factors, trapping platelets, and restricting blood flow (producing ischemic tissue damage).
Excess thrombin from coagulation results in conversion of plasminogen to plasmin, which cleaves the fibrin thrombi (fibrinolysis) creating fibrin split products and promotes proteolysis of clotting components. The fibrin degradation products (FDPs) in turn exhibit anticoagulant properties, including preventing thrombin production. The net outcome is uncontrollable bleeding. Patients may bleed from any breaks in the skin or mucous membranes. Laboratory results will demonstrate increased PT and PTT, decreased fibrinogen, thrombocytopenia, prolonged bleeding time, increased D-dimer, and presence of FDPs. Fibrin thrombi cause damage to RBC membranes producing a normocytic anemia with schistocytes and reticulocytosis (microangiopathic hemolytic anemia).

Pathology - ​Factor V Leiden Thrombophilia
Deep venous thrombosis (DVT) in left femoral vein may arise due to factor V Leiden thrombophilia. It is an autosomal dominant inherited disease and the most common hereditary hypercoagulability illness.
Family history will likely be positive for venous thromboembolic events (DVT or pulmonary embolism). The condition is a result of mutant clotting factor V that is unable to be destroyed by protein C. Uninhibited factor V activity promotes thrombin production, leading to excess fibrin and excessive coagulation. Patients will likely not have risk factors normally associated with venous thromboembolism, such as prolonged stasis (e.g., recent surgery, long flights, sedentary jobs), hypercoagulability (e.g., malignancy, oral contraceptives, pregnancy), or injury to vasculature (e.g., age, trauma, smoking). The most typical area for clots to form is in veins around the calf; however, advancement to femoral veins is often much more symptomatic. aPC would ordinarily contribute to prolonged coagulation times (aPTT) but will not have this effect in factor V Leiden people. Dilute Russell’s viper venom time may also be used to diagnose factor V Leiden.
Clinically, patients with DVT may suffer local soreness to palpation, pain with movement, erythema, warmth, and edema, which may be similar to cellulitis; however, patients with infection will often have a higher fever. Ultrasonography will often pinpoint the thrombus location.