A girl on sulphonamides developed abdominal pain and presented to emergency with a seizure. What is the probable cause?
**Core Concept**
Sulphonamides are a class of antimicrobials that inhibit bacterial synthesis of folic acid by competing with para-aminobenzoic acid (PABA) for the enzyme dihydropteroate synthase. This action leads to a deficiency in tetrahydrofolic acid, essential for DNA synthesis in rapidly dividing microorganisms.
**Why the Correct Answer is Right**
The patient's symptoms suggest aseptic meningitis, which is a rare but serious side effect of sulphonamide therapy. This is due to the inhibition of dihydrofolate reductase in the brain, leading to a decrease in tetrahydrofolate levels. Tetrahydrofolate is essential for the synthesis of neurotransmitters, such as serotonin, and its deficiency can cause neurological symptoms, including seizures.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while sulphonamides can cause allergic reactions, they are not typically associated with seizures.
**Option B:** This option is incorrect because while sulphonamides can cause gastrointestinal side effects, they are not typically associated with seizures.
**Option C:** This option is incorrect because while sulphonamides can cause neurological symptoms, such as ataxia and confusion, seizures are not a typical presentation.
**Clinical Pearl / High-Yield Fact**
Sulphonamide-induced aseptic meningitis is a rare but serious side effect of sulphonamide therapy, and its diagnosis requires a high index of suspicion.
**Correct Answer:** C. **Sulphonamide-induced aseptic meningitis.**