**Question:** Chaga's disease is caused by: September 2011

**Core Concept:** Chaga's disease is a fungal infection caused by the inhalation of spores of the fungus **Inonotus obliquus** (formerly known as **Tuberkuloses puteana**). This fungus is an **endophytic basidiomycete** commonly found in birch trees.

**Why the Correct Answer is Right:** Chaga's disease, also known as Chaga's inflammatory mycosis, is primarily caused by the inhalation of spores from the fungus **Inonotus obliquus**. This fungus is endophytic, meaning it lives within plant tissues without causing harm to the host. In the case of Chaga's disease, it infects the lungs and results in an inflammatory response, leading to the clinical manifestations of the condition.

**Why Each Wrong Option is Incorrect:**

A. **Ichthyosis:** This refers to a group of genetic skin disorders characterized by dry, scaly skin, not a fungal infection caused by inhaled spores.

B. **Pneumonia:** Although Chaga's disease can cause pneumonia, the correct answer should specifically mention the causative agent, i.e., **Inonotus obliquus**.

C. **Cryptococcosis:** This refers to infections caused by the fungus **Cryptococcus**, not **Inonotus obliquus**.

D. **Histoplasmosis:** Histoplasmosis is caused by the fungus **Histoplasma capsulatum**, not **Inonotus obliquus**.

**Clinical Pearl:** Chaga's disease, also known as chagas disease, is a rare and underreported fungal infection affecting the lungs. It is endemic in some parts of Russia, Ukraine, and Eastern European countries, where the birch trees, the primary habitat of **Inonotus obliquus**, are prevalent. This fungus can lead to respiratory symptoms, such as cough, shortness of breath, and chest pain, often presenting as a chronic pulmonary condition.

**Correct Answer:** Chaga's disease is caused by the inhalation of spores from the endophytic fungus **Inonotus obliquus**, which is endemic in certain regions with a high birch tree population.