Amino Acids in Pediatric Medicine

A comprehensive guide for pediatricians and medical students focusing on amino acid disorders, functions, and clinical relevance.

Essential Amino Acids

Phenylalanine (Phe)

Overview

Primary Functions:

• Precursor for tyrosine
• Essential for neurotransmitter synthesis
• Required for protein synthesis

Associated Disorders:

• Phenylketonuria (PKU)
  • Incidence: 1:10,000-15,000 births
  • Screening: Part of newborn screening programs
  • Management: Low-Phe diet, medical foods
• Hyperphenylalaninemia

Clinical Manifestations	Monitoring Parameters
- Developmental delay - Seizures - Fair skin/hair - Behavioral problems	- Blood Phe levels - Growth parameters - Development milestones - Dietary compliance

Tryptophan (Trp)

Overview

Primary Functions:

• Serotonin synthesis
• Melatonin production
• Niacin synthesis

Associated Disorders:

• Hartnup Disease
  • Incidence: 1:30,000 births
  • Inheritance: Autosomal recessive
  • Management: Niacin supplementation, sun protection
• Tryptophan Hydroxylase Deficiency

Clinical Manifestations	Monitoring Parameters
- Pellagra-like rash - Cerebellar ataxia - Mood disorders - Sleep disturbances	- Plasma tryptophan - Urinary amino acids - Growth monitoring - Neurological assessment

Lysine (Lys)

Overview

Primary Functions:

• Collagen formation
• Carnitine synthesis
• Calcium absorption

Associated Disorders:

• Hyperlysinemia
  • Rare genetic disorder
  • Variable clinical significance
  • Management: Monitoring
• Lysinuric Protein Intolerance (LPI)

Clinical Manifestations	Monitoring Parameters
- Growth failure - Osteoporosis - Muscle weakness - Hepatosplenomegaly	- Plasma lysine - Bone density - Growth charts - Organ function tests

Non-Essential Amino Acids

Tyrosine (Tyr)

Overview

Primary Functions:

• Catecholamine synthesis
• Melanin production
• Thyroid hormone synthesis

Associated Disorders:

• Tyrosinemia
  • Type I (most severe)
  • Type II (oculocutaneous)
  • Type III (rare)
• Alkaptonuria

Clinical Manifestations	Monitoring Parameters
- Liver failure - Renal tubular dysfunction - Eye lesions - Growth failure	- Blood tyrosine - Liver function - Renal function - Ophthalmological exam

Branched-Chain Amino Acids (BCAAs)

Leucine (Leu)

Overview

Primary Functions:

• Protein synthesis stimulation
• Blood sugar regulation
• Growth hormone production
• Wound healing

Associated Disorders:

• Maple Syrup Urine Disease (MSUD)
  • Incidence: 1:185,000 births
  • Acute metabolic decompensation
  • Emergency protocol required
• Isovaleric Acidemia

Clinical Manifestations	Monitoring Parameters
- Maple syrup odor in urine - Lethargy/coma - Feeding difficulties - Developmental delay	- BCAA levels - Ketones - Brain MRI - Growth parameters

Valine (Val)

Overview

Primary Functions:

• Muscle metabolism
• Cognitive function
• Immune system support

Associated Disorders:

• MSUD (with Leucine and Isoleucine)
  • Neurological complications
  • Dietary management essential

Clinical Manifestations	Management Approach
- Poor feeding - Neurological symptoms - Growth issues - Metabolic acidosis	- Medical formula - Protein restriction - Emergency protocols - Regular monitoring

Isoleucine (Ile)

Overview

Primary Functions:

• Hemoglobin synthesis
• Blood sugar regulation
• Muscle metabolism

Associated Disorders:

• MSUD Component
  • Part of branched-chain organic acidemias
  • Neonatal screening target

Monitoring Aspects	Therapeutic Approaches
- Plasma levels - Nutritional status - Development tracking - Metabolic stability	- BCAA-free formula - Sick-day protocols - Dietary planning - Metabolic team follow-up

Sulfur-Containing Amino Acids

Methionine (Met)

Overview

Primary Functions:

• SAM-e synthesis
• Protein synthesis initiation
• Homocysteine metabolism
• Antioxidant production

Associated Disorders:

• Homocystinuria
  • Incidence: 1:200,000-335,000
  • CBS deficiency
  • Thrombotic risk
• MTHFR Deficiency

Clinical Manifestations	Monitoring Parameters
- Marfanoid features - Lens dislocation - Thromboembolism - Developmental delay	- Homocysteine levels - Methionine levels - Ophthalmologic exam - Clotting studies

Cysteine (Cys)

Overview

Primary Functions:

• Glutathione synthesis
• Taurine production
• Disulfide bond formation
• Detoxification

Associated Disorders:

• Cystinuria
  • Incidence: 1:7,000
  • Kidney stones
  • Renal damage risk
• Cystinosis

Clinical Manifestations	Management Approach
- Renal stones - Growth failure - Crystal arthropathy - Fanconi syndrome	- Hydration therapy - Urinary alkalinization - Dietary modification - Stone prophylaxis

Essential Amino Acids (continued)

Histidine (His)

Overview

Primary Functions:

• Hemoglobin synthesis
• Histamine production
• pH buffer in blood
• Growth and repair of tissues

Associated Disorders:

• Histidinemia
  • Incidence: 1:8,000
  • Generally benign
  • Speech delays reported
• Urocanic aciduria

Clinical Manifestations	Monitoring Parameters
- Speech delay - Learning difficulties - Behavioral changes - Generally asymptomatic	- Plasma histidine - Urocanic acid - Development screening - Speech assessment

Threonine (Thr)

Overview

Primary Functions:

• Collagen and elastin formation
• Fat metabolism
• Immune system support
• Intestinal mucin production

Associated Disorders:

• Threonine Dehydratase Deficiency
  • Very rare condition
  • Neurological impact
  • Developmental concerns

Clinical Manifestations	Management Approach
- Developmental delay - Spasticity - Seizures - Failure to thrive	- Dietary supplementation - Neurological monitoring - Growth tracking - Physical therapy

Conditionally Essential Amino Acids

Arginine (Arg)

Overview

Primary Functions:

• Nitric oxide synthesis
• Urea cycle
• Growth hormone secretion
• Wound healing

Associated Disorders:

• Urea Cycle Disorders
  • Incidence: 1:35,000
  • Hyperammonemia
  • Emergency protocols needed
• Arginase Deficiency

Clinical Manifestations	Monitoring Parameters
- Hyperammonemia - Neurological symptoms - Protein aversion - Developmental delay	- Ammonia levels - Plasma amino acids - Neurological status - Growth parameters

Glutamine (Gln)

Overview

Primary Functions:

• Intestinal cell fuel
• Immune system support
• Acid-base balance
• Nitrogen transport

Associated Disorders:

• Glutamine Synthetase Deficiency
  • Extremely rare
  • Severe brain malformations
  • Multi-organ involvement
• Secondary deficiencies in critical illness

Clinical Manifestations	Therapeutic Approaches
- Seizures - Brain malformations - Multi-organ dysfunction - Metabolic acidosis	- Supplementation - Anticonvulsants - Supportive care - Nutritional support

Non-Essential Amino Acids with Clinical Significance

Glycine (Gly)

Overview

Primary Functions:

• Collagen formation
• Neurotransmitter function
• Heme synthesis
• Bile acid conjugation

Associated Disorders:

• Nonketotic Hyperglycinemia
  • Incidence: 1:60,000
  • Severe neurological impact
  • Poor prognosis
• Glycine Encephalopathy

Clinical Manifestations	Management Approach
- Neonatal seizures - Hypotonia - Respiratory issues - Lethargy/coma	- Sodium benzoate - Dextromethorphan - Seizure control - Respiratory support

Disclaimer

The notes provided on Pediatime are generated from online resources and AI sources and have been carefully checked for accuracy. However, these notes are not intended to replace standard textbooks. They are designed to serve as a quick review and revision tool for medical students and professionals, and to aid in theory exam preparation. For comprehensive learning, please refer to recommended textbooks and guidelines.