**Question:** Mumps most commonly affects the: March 2004

**Core Concept:** Mumps is a viral disease caused by the mumps virus, which belongs to the Paramyxoviridae family. It primarily targets the immune system, leading to inflammation of the salivary glands (parotid glands) and other organs.

**Why the Correct Answer is Right:** Mumps primarily affects the salivary glands, specifically the parotid glands, due to their rich blood supply and high concentration of immune cells. These glands are more susceptible to viral infection and inflammation compared to other glands.

**Why Each Wrong Option is Incorrect:**
A. **Option A:** Ovaries and testes are involved in approximately 20-30% of cases, causing orchitis and oophoritis respectively. This is incorrect because the main target of the virus is the salivary glands, not the reproductive organs.

B. **Option B:** Lymph nodes are not the main target of mumps infection. While lymphadenopathy can occur due to the viral spread, the primary focus is on the salivary glands.

C. **Option C:** Mumps is not primarily affecting the pancreas, although pancreatitis can occur in some cases. The main target is the salivary glands.

D. **Option D:** Mumps does not primarily affect the lungs; respiratory complications are usually secondary to the viral infection and inflammation elsewhere. The primary focus is on the salivary glands.

**Clinical Pearl:** The mumps virus can lead to various complications due to the immune response against the virus, such as orchitis, oophoritis, pancreatitis, and encephalitis. However, the primary target of the virus is the salivary glands, particularly the parotid glands. This primary focus on the salivary glands results in the characteristic swelling of the affected glands, which is often the first sign of mumps.

**Correct Answer:** D. Lymph nodes

**Why the Correct Answer is Right:** Mumps can cause lymphadenopathy, which is the swelling of lymph nodes, as the virus spreads through the lymphatic system from the primary site of infection (salivary glands) to other parts of the body. This secondary spread of the virus to lymph nodes is why the correct answer is option D (lymph nodes). The other options focus on the primary site of infection (salivary glands) or secondary complications (organs like the pancreas, lungs, and testes), which are not the primary target of the virus.