Which substance is classically associated with an anion gap metabolic acidosis with osmolar gap and optic toxicity?

Which substance is classically associated with an anion gap metabolic acidosis with osmolar gap and optic toxicity?

• A. Methanol
• B. Ethylene glycol
• C. Uremia
• D. Lactic acidosis

Answer: (A)

Methanol poisoning is classically linked to a high anion gap metabolic acidosis, an osmolar gap, and optic toxicity. The osmolar gap comes from unmetabolized methanol in the blood, which makes the measured osmolality higher than calculated. Metabolically, methanol is converted by alcohol dehydrogenase to formaldehyde and then formic acid; the accumulation of formic acid drives the anion gap metabolic acidosis and damages the optic nerve, leading to visual disturbances that can be severe. Ethylene glycol can also cause an osmolar gap with anion gap acidosis, but optic toxicity is not the hallmark feature; it more characteristically causes CNS effects and oxalate nephrosis. Uremia and lactic acidosis produce anion gap acidosis without the classic osmolar gap or optic neuropathy. So the combination of optic toxicity with anion gap acidosis and osmolar gap specifically points to methanol.

Methanol poisoning is classically linked to a high anion gap metabolic acidosis, an osmolar gap, and optic toxicity. The osmolar gap comes from unmetabolized methanol in the blood, which makes the measured osmolality higher than calculated. Metabolically, methanol is converted by alcohol dehydrogenase to formaldehyde and then formic acid; the accumulation of formic acid drives the anion gap metabolic acidosis and damages the optic nerve, leading to visual disturbances that can be severe.

Ethylene glycol can also cause an osmolar gap with anion gap acidosis, but optic toxicity is not the hallmark feature; it more characteristically causes CNS effects and oxalate nephrosis. Uremia and lactic acidosis produce anion gap acidosis without the classic osmolar gap or optic neuropathy.

So the combination of optic toxicity with anion gap acidosis and osmolar gap specifically points to methanol.