A 4-month-old child presents with excessive irritability & crying, unexplained hyperpyrexia, vomiting, difficulty feeding for last 15 days. On admission he has rigidity & visual inattentiveness; CT scan brain shows the following finding. What is the probable diagnosis?
**Core Concept**
Krabbe disease is a rare, inherited disorder caused by a deficiency of the enzyme galactocerebroside beta-galactosidase (GALC), leading to accumulation of galactosylceramide and psychosine in the brain, causing demyelination and severe neurological damage.
**Why the Correct Answer is Right**
The accumulation of psychosine in Krabbe disease is toxic to oligodendrocytes, the cells responsible for myelination in the central nervous system. This results in rapid demyelination, particularly in the white matter of the brain. The infant's symptoms, including excessive irritability, hyperpyrexia, vomiting, and visual inattentiveness, are consistent with the progression of Krabbe disease. The CT scan brain finding is likely to show diffuse white matter changes, with or without periventricular calcifications.
**Why Each Wrong Option is Incorrect**
**Option A:** Alexander disease is a rare degenerative disease caused by a mutation in the GFAP gene, leading to accumulation of astrocytic intermediate filaments in the brain, primarily affecting the white matter. It presents with megalencephaly, developmental delay, and seizures, which do not match the infant's symptoms.
**Option C:** Metachromatic Leukodystrophy is another inherited disorder caused by a deficiency of the enzyme arylsulfatase A, leading to accumulation of sulfatides in the brain and peripheral nerves. It typically presents with a more gradual onset of symptoms, including gait disturbance, weakness, and visual loss.
**Option D:** Adrenoleukodystrophy is a genetic disorder affecting the X chromosome, characterized by accumulation of very-long-chain fatty acids in the adrenal glands and brain. It primarily affects males and presents with adrenal insufficiency, demyelinating disease, and seizures.
**Clinical Pearl / High-Yield Fact**
Krabbe disease is a rapidly progressing disorder, with most infants dying within 2 years of onset. Early diagnosis through genetic testing or enzyme assays is crucial for families to prepare for the child's prognosis.
**✓ Correct Answer: B. Krabbe disease**