**Question:** Disseminated intravascular coagulation (DIC) differs from thrombotic thrombocytopenic purpura. In this reference the DIC is most likely characterized by -

A. Thrombocytopenia and increased fibrin degradation products (FDP)
B. Thrombocytopenia and increased D-dimer levels
C. Thrombocytopenia and elevated lactate dehydrogenase (LDH)
D. Thrombocytopenia and decreased fibrinogen levels

**Correct Answer:**

**Core Concept:** Disseminated intravascular coagulation (DIC) and thrombotic thrombocytopenic purpura (TTP) are both bleeding disorders associated with platelet dysfunction, but they differ in their key laboratory findings.

**Why the Correct Answer is Right:**

DIC is a complex coagulation disorder characterized by excessive activation of the coagulation cascade, leading to widespread microvascular thrombosis, and subsequent organ dysfunction. The correct answer (D) indicates the laboratory findings most characteristic of DIC: thrombocytopenia (decreased platelet count) and decreased fibrinogen levels (an essential clotting factor).

In contrast, TTP is caused by a deficiency of the enzyme ADAMTS13, which normally cleaves ultra-large von Willebrand factor (vWF) multimers. Thrombocytopenia is the hallmark of TTP, but the key laboratory abnormality is a very low plasma ADAMTS13 activity level.

**Why Each Wrong Option is Incorrect:**

A: This option incorrectly highlights increased fibrin degradation products (FDP) as the primary finding in DIC, which is not the most prominent feature.

B: While DIC is associated with increased D-dimer levels, it is not specific to DIC and can also be elevated in other conditions like deep vein thrombosis or pulmonary embolism.

C: Elevated lactate dehydrogenase (LDH) can be seen in various conditions, not limited to DIC, making it a less specific marker for this disorder.

**Clinical Pearl:**

DIC and TTP are distinct conditions with different underlying pathophysiology and clinical presentations. Understanding the specific laboratory findings of each helps in accurate diagnosis and appropriate management.