Which of the following is the most common amino aciduria in the Indian population?

Explanation

## Epidemiology of Amino Acidurias **Key Point:** Phenylketonuria (PKU) is the most common amino aciduria worldwide, with an incidence of approximately 1 in 10,000 to 1 in 15,000 live births globally. In India, PKU remains the most frequently detected inborn error of amino acid metabolism on newborn screening programs. ### Comparative Incidence Table | Amino Aciduria | Incidence (Global) | Inheritance | Enzyme Defect | | --- | --- | --- | --- | | **Phenylketonuria** | 1 in 10,000–15,000 | Autosomal recessive | Phenylalanine hydroxylase | | Alkaptonuria | 1 in 250,000–1 in 1,000,000 | Autosomal recessive | Homogentisate 1,2-dioxygenase | | Maple syrup urine disease | 1 in 185,000 | Autosomal recessive | Branched-chain α-ketoacid dehydrogenase | | Homocystinuria | 1 in 200,000–1 in 335,000 | Autosomal recessive | Cystathionine β-synthase | ### Clinical Features of PKU **High-Yield:** PKU presents with: - Intellectual disability (if untreated) - Eczema and fair skin - Musty or "mousy" odor of urine (due to phenylacetic acid) - Seizures in untreated cases - Behavioral problems ### Why PKU Is Most Common 1. **Carrier frequency:** Higher frequency of heterozygous carriers in the general population 2. **Newborn screening:** PKU is screened universally in most developed and many developing nations, including India, leading to early detection 3. **Biochemical basis:** The enzyme phenylalanine hydroxylase is ubiquitously expressed; mutations are relatively common **Clinical Pearl:** Early diagnosis through newborn screening (Guthrie test or tandem mass spectrometry) and initiation of a phenylalanine-restricted diet within the first few weeks of life can prevent intellectual disability entirely. **Mnemonic:** **PHEN** = **P**henylketonuria is the **H**ighest **E**ncountered **N**eonatal amino aciduria.