**Question:** Consecutive optic atrophy is seen in -

A. Progressive external ophthalmoplegia
B. Kearns Sayre syndrome
C. MELAS syndrome
D. Leber hereditary optic neuropathy

**Core Concept:** Consecutive optic atrophy refers to a group of mitochondrial disorders characterized by optic atrophy, which is a condition involving the degeneration of the optic nerve, leading to vision loss. These conditions are caused by mutations in mitochondrial DNA (mtDNA). Mitochondrial disorders are often associated with a combination of clinical features, resulting in a syndrome.

**Why the Correct Answer is Right:** Optic atrophy is a manifestation of mitochondrial dysfunction, and consecutive optic atrophy is seen in specific syndromes associated with mtDNA mutations. In this case, the correct answer is D (Leber hereditary optic neuropathy), a mitochondrial disorder characterized by bilateral optic nerve degeneration. mtDNA mutations cause a decreased energy production in the mitochondria, leading to oxidative stress and cell damage, including optic nerve cells.

**Why Each Wrong Option is Incorrect:**

A. Progressive external ophthalmoplegia (PEO) is a syndrome characterized by muscle weakness involving the eye muscles, but it is not specifically related to optic atrophy.
B. Kearns Sayre syndrome includes optic atrophy and pigmentary retinopathy, but it primarily affects children and has a more severe phenotype than consecutive optic atrophy.
C. Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome involves a combination of neurological symptoms but does not specifically focus on optic atrophy.

**Clinical Pearl:**

Understanding consecutive optic atrophy syndromes is crucial for diagnosing and managing patients with mitochondrial disorders. By recognizing these syndromes, clinicians can identify the underlying mtDNA mutations, enabling appropriate genetic counseling and potential treatment options. Additionally, knowledge of these syndromes can help differentiate them from other optic atrophy etiologies, such as inflammatory or ischemic optic neuropathies, and ensure appropriate management and prognosis.