**Question:** Histology of a specimen shows Mikulicz cells and Russell bodies. These are characteristic of:

**Core Concept:** Mikulicz cells are large, foamy histiocytes found in the tissues of patients with systemic lupus erythematosus (SLE). Russell bodies are autolysosomes containing digested material, typically seen in activated macrophages. Both findings are indicative of a situation where macrophages are activated and engulfing cellular debris.

**Why the Correct Answer is Right:** In this case, the presence of Mikulicz cells and Russell bodies in a histology specimen is indicative of systemic lupus erythematosus (SLE). In SLE, these cells serve as markers for tissue involvement and macrophage activation.

**Why Each Wrong Option is Incorrect:**

A. Systemic sclerosis (scleroderma): While Mikulicz cells can be seen in scleroderma, Russell bodies are not typically observed.
B. Sarcoidosis: Similar to option A, Mikulicz cells can be present, but the absence of Russell bodies makes this incorrect.
C. Systemic sclerosis (scleroderma): As mentioned before, the absence of Russell bodies is a distinguishing feature that makes this incorrect.
D. Lupus erythematosus: Although Mikulicz cells can be seen in lupus erythematosus, the presence of Russell bodies is more consistent with SLE.

**Clinical Pearl:** The presence of Mikulicz cells and Russell bodies together represents a distinctive histopathological feature of systemic lupus erythematosus (SLE) and is often used to aid in the diagnosis of this condition.

**Correct Answer:** D. Lupus erythematosus

**Explanation:** The correct answer is option D ("Lupus erythematosus"), as it is the only option among the given options where the presence of Mikulicz cells and Russell bodies is consistent. In systemic lupus erythematosus (SLE), these cells and bodies are indicative of macrophage activation and tissue involvement.