This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
A 5-day-old child presents with intractable seizures. He had rashes all over the body. Blood examination showed hyperammonemia and lactic acidosis. The probable diagnosis is – 
Select and explain. 
A. Organic aciduria, B. Mitochondrial encephalopathy with lactic aciduria, C. Phenylketonuria, D. Urea cycle enzyme deficiency
A: Organic aciduria
Answer: A: Organic aciduria 
Explanation: Organic aciduria (organic acidemia)

Organic aciduria is a term used to classify a group of metabolic disorders which disrupt normal amino acid metabolism, particularly branched-chain amino acids (isoleucine, leucine, valise) causing a build of acids which are usually not present.
The main types of organic acidemia are : -

i) Methylnzalonic acidemia    
ii) Propionic acidenzia       
iii) Isoavleric acidemia
iv) Maple syrup urine disease
vi) Giutaric acidemia           
v) Combined (multiple) carboxylase deficiency
Clinical manifestations

Neurological damage → Mental retardation, Seizures, Lethargy, Vomiting.
Developmental delay               
Hypoglycemia                           
Ketoacidosis        
Malnutrition     
Hypotonia     
Hyperammonemia     
Poor feeding and slow growth  
Metabolic acidosis (Lactic acidosis)  
Rash, alopecia and ataxia in some organic aciduria.            

Mitochondrial encephalopathy (MELAS)

Encephalopathy
Lactic acidosis
Stroke-like episodes → Blindness, paralysis, vomiting.

Disorders of the urea cycle

Ammonia is mostly derived from the catabolism of amino acid and is converted to an amino group in urea by enzymes of the urea cycle.
So, defects in enzymes of urea cycle cause →

i) Hyperammonemia           
ii) Encephalopathy     
iii) Vomiting