## Core Concept
Sarcoidosis is a systemic granulomatous disease characterized by the formation of non-caseating granulomas in various organs, most commonly the lungs, lymph nodes, skin, and eyes. The etiology of sarcoidosis remains unknown, but it is believed to result from a combination of genetic and environmental factors leading to an exaggerated immune response. The disease can manifest with a wide range of symptoms depending on the organs involved.

## Why the Correct Answer is Right
Hypercalcemia is a recognized complication of sarcoidosis. It occurs due to the abnormal regulation of vitamin D. In sarcoidosis, **macrophages** within granulomas express **1-alpha-hydroxylase**, an enzyme that converts 25-hydroxyvitamin D into its active form, 1,25-dihydroxyvitamin D (calcitriol). Calcitriol enhances intestinal absorption of calcium and can lead to hypercalcemia. This mechanism is key to understanding why hypercalcemia is associated with sarcoidosis.

## Why Each Wrong Option is Incorrect
- **Option A:** Sarcoidosis can cause **hypercalcemia** as explained, making this option incorrect as an "except" answer.
- **Option B:** The disease can lead to **erythema nodosum**, a type of skin inflammation that presents as tender, red nodules, typically on the shins. This is a known manifestation of sarcoidosis.
- **Option C:** Sarcoidosis can cause **bilateral hilar lymphadenopathy**, which is a classic radiographic finding, often seen on chest X-rays.

## Why Option D is Correct
- **Option D:** Sarcoidosis does not typically cause **hypocalcemia**. Given the mechanism described, where there's an increased production of active vitamin D leading to increased absorption of calcium, **hypocalcemia** (low calcium levels) is not a characteristic feature of sarcoidosis.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that sarcoidosis can mimic many other diseases due to its wide range of manifestations. However, the presence of **non-caseating granulomas** on biopsy and an elevated level of **angiotensin-converting enzyme (ACE)**, particularly in bronchoalveolar lavage fluid or serum, can support the diagnosis.

## Correct Answer: D. hypocalcemia