• Growth: Physical maturation, quantitative change (increase in size/number of cells/intracellular substance).
• Development: Functional and physiological maturation, qualitative change (progressive increase in skill, related to maturation and myelination of nervous system).
• Genetic Factors: Sex, Nationality, Race. Genetic predisposition is the most important factor affecting growth and development.
• Prenatal Factors (Intrauterine environment): Maternal nutrition, maternal infection, maternal substance abuse, maternal illness, hormones, misalliance.
• Postnatal Factors: Growth potential, Nutrition, childhood illness, physical/psychological environment, socioeconomic status, climate, birth order of the child, intelligence.

• Weight Estimation (Weech's Formula): Child weighed nude on electronic scale. Spring balance is less accurate.
  • 3-12 months: (Age in months + 9) / 2
  • 1-6 years: (Age in years x 2) + 8
  • 7-12 years: ((Age in years x 7) - 5) / 2
• Length vs Height: Length is for children < 2 years (child supine on rigid table/infantometer, legs straightened). Height is for > 2 years (child stands upright on stadiometer, head held in Frankfurt's plane - line joining floor of external auditory meatus to floor of orbit is horizontal).
• Crown Rump Length: Length from vertex to ischial tuberosity.
• Head Circumference (HC): Maximum circumference from occipital protuberance to forehead.
• Chest Circumference (CC): Measured at level of nipples midway between inspiration & expiration in recumbent position.
• Body Proportions (Upper Segment:Lower Segment Ratio):
  • At birth: 1.7 : 1
  • At 3 years: 1.3 : 1
  • At 6-7 years: 1 : 1
• Mid Arm Circumference (MAC): Relatively constant between 1-5 years (Age independent). Normal is 16.0 - 17.5 cm. < 12.5 cm indicates a malnourished child.
• Z scores: Standard deviations from the median reference.

• Weight Progression: Average Birth Weight (BW) = 3 kg. Loses 10% of body weight initially, regains BW by 10 days. Gains 25-30 gm/day for 1st 3 months, then 400 gm/month till end of 1st year.
  • Doubles at: 5 months
  • Triples at: 1 year
  • Quadruples (4x) at: 2 years
  • 6x at: 5 years
  • 10x at: 10 years
• Height Progression: At birth = 50 cm. 60 cm at 3 months.
  • 1 year: 75 cm
  • 4 years: 100 cm (doubles birth length)
  • Gain 5 cm/year till 10 years.
• Head Circumference (HC) Progression: At birth = 35 cm.
  • 3 months: 40 cm
  • 12 months: 45 cm
  • 24 months: 48 cm
  • 12 years: 52 cm
• Chest Circumference: 3 cm less than HC at birth. Becomes equal to HC at 1 year. After 1 year, exceeds HC by 2 cm each year.

1. Gross Motor

• Tested in: Ventral Suspension (Newborn flops, 4-12 wks brings head above plane), Supine (Newborn has head lag, 16-20 wks head ahead with back straight).
• 3 months: Neck holding, pulls to sit with NO head lag. Lifts head and upper chest in prone.
• 4 months: Bears weight on legs, asymmetric tonic neck reflex gone.
• 5 months: Sitting with support, rolls front to back.
• 8 months: Sitting steadily without support (back straight), crawls.
• 9 months: Pulls to stand with furniture.
• 10 months: Cruising (walking holding furniture), pulls from supine to sitting.
• 12-14 months: Walking without support.
• 15 months: Walks sideways/backwards, creeps up stairs.
• 18 months: Running stiffly, sits on small chair.
• 2 years (24 mo): Climbs stairs (2 feet per step), opens doors, jumps.
• 3 years: Climbs upstairs (alternating, 1 foot per step), rides tricycle, stands on 1 foot.
• 4 years: Climbs down stairs (1 foot per step), hops on one foot.
• 5 years (60 mo): Skips.

2. Fine Motor / Adaptive

• 3 months: Brings hands together in midline, follows object 180 degrees. Binocular vision (3-6 mths).
• 4 months: Palmar grasp gone, reaches for objects, tries to grasp red ring.
• 6 months: Transfers objects hand to hand, radial grasp.
• 8 months: Thumb-finger grasp.
• 10 months: Pincer grasp (picks up pellet with assisted movement).
• 12 months (1 yr): Unassisted pincer movement, turns pages of book (2-3 at a time).
• 15 months: Tower of 3 cubes, inserts raisin in bottle.
• 18 months: Tower of 4 cubes, feeds self from cup, imitates vertical stroke.
• 2 years (24 mo): Tower of 6-7 cubes, turns book pages 1 by 1, copies vertical line.
• 3 years: Tower of 9-10 cubes, copies circle.
• 4 years: Copies cross and rectangle/square, draws man with 2-4 parts besides head.
• 5 years: Copies triangle.

3. Social & Personal

• 1 month: Regards face of mother.
• 2 months: Social smile in response to face.
• 3 months: Recognizes mother/caretaker.
• 6-7 months: Enjoys mirror, inhibits to "no".
• 8-9 months: Separation anxiety, waves bye-bye.
• 10 months: Plays peek-a-boo, points to objects.
• 18-24 months: Indicates toilet needs, helps undress, kisses parent with pucker.
• 3 years: Parallel play with other children.
• 4 years: Social interaction and role-playing, goes to toilet alone.

4. Language

• 1 month: Turns head to sound.
• 6 months: Monosyllabic babble.
• 10 months: "mama", "dada" with meaning, understands spoken speech, follows one-step command.
• 12 months: Speaks first real word.
• 18 months: 10-20 words, identifies body parts.
• 2 years: Joins 2-3 words in a short sentence, pronoun "I".
• 3 years: 250 words, knows age and sex.
• 4 years: Tells a story, counts 4 pennies accurately.

Bowel & Bladder Control: Early months driven by gastrocolic reflex. At 7 months, no relation to feeds. Toilet trainable between 18 months - 2 years.

• Gastroenteritis: Inflammation of stomach and intestines characterized by vomiting, diarrhea, and abdominal pain.
• Diarrhea: Passage of ≥3 loose or watery stools per day. In infants, consistency (watery) is more diagnostic than frequency. Passing "pasty" stools by breastfed young infants is normal.
• Dysentery: Small-volume, frequent bloody stools with mucus, tenesmus, urgency (predominant symptom of colitis).
• Acute Diarrhea: < 14 days (mostly infectious).
• Persistent Diarrhea: ≥ 14 days (prolonged infection/malnutrition).
• Chronic Diarrhea: > 4 weeks (non-infectious: celiac, Inflammatory Bowel Disease).

• Viral: Rotavirus (leading cause in young children), Norovirus, Adenovirus, Astrovirus, Enteric adenovirus.
• Bacterial: Escherichia coli (ETEC, EHEC), Salmonella (non-typhoid and typhi), Shigella spp, Campylobacter jejuni, Vibrio cholerae.
• Parasitic: Giardia lamblia, Entamoeba histolytica, Cryptosporidium parvum.
• Non-infectious: Food intolerance (lactose), cow's milk protein allergy, Celiac disease, Inflammatory bowel disease (IBD), Antibiotic-associated diarrhea.

1. Osmotic Diarrhea: Due to poorly absorbed solutes (e.g., lactose intolerance). Caused by glucose-galactose malabsorption, disaccharidase deficiencies (lactase, sucrase), excess carbonated fluids, unabsorbable solutes (Sorbitol, Lactulose, Magnesium hydroxide).

2. Secretory Diarrhea: Excessive secretion. Activation of intracellular mediators (cyclic Adenosine Monophosphate (cAMP), cGMP, intracellular calcium) stimulates active chloride secretion from crypt cells and inhibits neutral coupled sodium chloride absorption.

• cAMP activation: Cholera, E. coli (heat-labile), Shigella, Salmonella, Campylobacter, Pseudomonas. Hormones: Vasoactive Intestinal Peptide (VIP), gastrin, secretin.
• cGMP activation: E. coli (heat-stable).
• Calcium dependent: Acetylcholine (Neurotransmitter).

Other mechanisms: Mutational Defects in Ion Transport (Na-H exchange, Cl-HCO3 exchange), Reduction in Surface Area (Short bowel syndrome, necrotizing enterocolitis), Alteration in Motility (malnutrition, scleroderma).

Dehydration is the loss of body water and electrolytes. Most volume loss is Extracellular Fluid (ECF) (plasma, lymph, interstitial fluid). Goal is to restore circulating blood volume -> interstitial fluid -> maintain continuing losses.

Severe Shock Signs: Weak/absent peripheral pulses, prolonged capillary refill >3 sec, tachycardia >120 bpm.

• Isonatremic (Isotonic): Serum Sodium 130-150 mmol/L. Equal loss of water & Na. Most common (~70%). Classic signs of dehydration.
• Hyponatremic (Hypotonic): Serum Sodium < 130 mmol/L. More Na loss than water. Fluid shifts from extracellular to intracellular space. Patients may appear less dehydrated but present with more severe shock and neurologic symptoms (seizures).
  DANGER: Overcorrection (>135mEq/L or >12mEq/L/24hr) causes Central Pontine Myelinolysis (CPM). Treat seizures with acute infusion of 3% Hypertonic Saline.
• Hypernatremic (Hypertonic): Serum Sodium > 150 mmol/L. More water loss than Na. Intravascular volume is partially protected by fluid shift from intracellular to extracellular space.
  Signs: Doughy skin, irritability, hypertonicity, high-pitched cry.
  MOST DANGEROUS FORM: High risk of Cerebral Hemorrhage and Thrombosis. Do not correct faster than 12mEq/L/24hr (correct over 2-4 days). Resuscitate with Normal Saline (NS). DO NOT use Lactated Ringer's (LR) as it is hypotonic and drops Na too fast.

• Plan A (No Dehydration): Treat at home. Oral Rehydration Solution (ORS) after each loose stool (<2 years: 50-100mL, 2-10 years: 100-200mL). Continue feeding.
• Plan B (Some Dehydration): ORS 75 mL/kg over 4 hours. Reassess after 4 hours. Replace ongoing losses.
• Plan C (Severe Dehydration/Shock): IV fluids (Ringer's Lactate or Normal Saline). Avoid IV fluids if malnourished or underlying cardiac/respiratory disease. Initial bolus 20 mL/kg over 30 min for shock.
  • < 12 months: 30 mL/kg in 1 hour, then 70 mL/kg in 5 hours (Total 6h).
  • ≥ 12 months: 30 mL/kg in 30 min, then 70 mL/kg in 2.5 hours (Total 3h).

Zinc Supplementation:
< 6 months: 10 mg/day for 10-14 days.
≥ 6 months: 20 mg/day for 10-14 days.

Antibiotics: ONLY for specific bacterial infections (Shigella, Cholera, Giardia, E. histolytica). Avoid in viral diarrhea.

Contraindications: Antimotility drugs (loperamide), starvation/prolonged fasting.

Holliday-Segar Method (Maintenance Fluids):

• Carbohydrates: Begins in mouth (salivary amylase) -> duodenum (pancreatic amylase breaks down starch/glycogen into maltose) -> brush border (maltase, sucrase, lactase break disaccharides to monosaccharides).
  Glucose/galactose absorbed across apical membrane by secondary active transport (Na+-glucose cotransporter). Fructose absorbed by facilitated diffusion.
• Proteins: Stomach (pepsin breaks proteins to short peptides) -> duodenum (trypsin, chymotrypsin, elastase from pancreas) -> peptidases break to single amino acids -> absorbed into bloodstream.
• Lipids: Mouth (lingual lipase) -> Stomach (gastric lipase) -> Small intestine (pancreatic lipase).
  Bile salts (have hydrophobic and hydrophilic sides) emulsify large lipid globules into small ones so lipases can act efficiently. Fatty acids and glycerides pass through plasma membrane into epithelial cells -> lymphatic vessels -> blood.
• Malabsorption Clinical Presentation: Diarrhea, abdominal distention, failure to thrive. Nutritional consequences are dramatic in young children due to limited energy reserves.
  • Explosive watery diarrhea: Carbohydrate malabsorption.
  • Loose and bulky stools: Celiac disease.
  • Pasty, pale-yellowish, offensive stools: Exocrine pancreatic insufficiency.
  • Watery, voluminous (like urine): Congenital chloride diarrhea.
  • Anorexia: Villous atrophy (celiac, post-infectious).
  • Excellent appetite: Pancreatic insufficiency.
  • Edema: Protein-losing enteropathy.
  • Digital clubbing: Cystic fibrosis, celiac disease.
  • Perianal/circumoral rash: Acrodermatitis enteropathica.

Initial work-up: Stool microscopy (Ova/Parasites like Giardia), stool occult blood/leukocytes, Complete Blood Count (CBC) with peripheral smear (microcytic anemia, lymphopenia, neutropenia, acanthocytosis).

• Carbohydrate Malabsorption:
  • Stool pH < 5.4 (acidic).
  • Clinitest (>2+ reducing substances).
  • Breath hydrogen test (Rise > 20 ppm above baseline is positive; patient must NOT be on antibiotics because colonic flora is essential for fermenting sugar).
  • Small bowel mucosal biopsy (disaccharidase assays).
• Fat Malabsorption:
  • 72-hour stool collection (Coefficient of Fat Absorption [CFA] normally ~90%).
  • Acid steatocrit test (reliable).
  • Sudan stain. Serum Vitamins A, D, E and Prothrombin Time (PT).
• Protein-Losing Enteropathy: Spot test for stool α1-antitrypsin (resistant to GI digestion unlike albumin). Hypoalbuminemia.
• Exocrine Pancreatic Function: Fecal elastase-1 (sensitive, specific, non-invasive, unaffected by exogenous pancreatic enzyme treatment, measured by ELISA). Sweat chloride test (Cystic Fibrosis). Gold standard: Direct analysis of duodenal aspirate.
• Intestinal Mucosal Disorders: Endoscopy and small bowel mucosal biopsy (multiple biopsies because involvement can be patchy).

• Definition: Permanent intolerance to gluten. T-cell mediated chronic inflammatory disorder with autoimmune/genetic components. Strong association with Human Leukocyte Antigen (HLA) DQ2 or DQ8 (>90%).
• Pathophysiology: Gluten (gliadin fraction) is resistant to digestion, sensitizes lamina propria lymphocytes, causing villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes in proximal small intestine. Takes weeks-years to develop or heal.
• Associated Conditions: Type 1 Diabetes, autoimmune thyroid disease, Down, Turner, Williams syndromes, IgA deficiency.
• Clinical: Mostly presents between 6mo - 2yr. Diarrhea, vomiting, distention, muscle wasting, anorexia, irritability.
  Extra-intestinal (High Yield): Iron deficiency anemia unresponsive to iron, osteoporosis, peripheral neuropathies, Dermatitis herpetiformis, dental enamel hypoplasia.
• Diagnosis:
  • Serology: Anti-tissue transglutaminase (anti-tTG) IgA is the test of choice (replaced anti-endomysial because it's cheaper and less operator dependent). Must check total IgA.
  • If anti-tTG > 10x normal -> check HLA DQ2/DQ8 and EMA. If positive, diagnosis is confirmed.
  • Intestinal biopsy is the Gold Standard (especially for asymptomatic or ambiguous cases).
• Treatment: Lifelong Strict Gluten-Free Diet (GFD) (< 50 mg/day). Delay/poor compliance increases risk of mortality and Non-Hodgkin lymphoma.

• Abetalipoproteinemia: Autosomal recessive mutation of microsomal triglyceride transfer protein.
  • Clinical: Severe fat malabsorption from birth, absent deep tendon reflexes and ataxia (due to severe Vitamin E deficiency), atypical retinitis pigmentosa.
  • Diagnosis: Acanthocytes in blood smear, extremely low cholesterol (<50 mg/dL), absent chylomicrons/VLDL.
  • Treatment: Massive doses of Vitamins A, D, E, K. Vitamin E (100-200 mg/kg/day) arrests neurologic degeneration.
• Microvillus Inclusion Disease: Autosomal recessive. Most commonly recognized cause of congenital diarrhea.
  • Clinical: Profuse watery secretory diarrhea at birth. Antenatal polyhydramnios.
  • Biopsy: Hypoplastic villous atrophy, no inflammatory infiltrate. Electron microscopy shows inclusion bodies.
  • Treatment: Fatal without Intestinal transplantation (definitive).
• Congenital Chloride Diarrhea: Defect in Na-Cl / HCO3 exchanger in ileal/colonic apical membrane.
  • Clinical: Life-threatening secretory diarrhea. Antenatal dilated bowel (misdiagnosed as obstruction).
  • Labs: Metabolic alkalosis, hypochloremia, hypokalemia, hyponatremia. Fecal Cl >90 mmol/L.
  • Treatment: Lifelong enteral substitution of KCl and NaCl.
• Acrodermatitis Enteropathica: Defect in apical protein for Zinc uptake.
  • Clinical: Symptoms soon after birth (bottle-fed) or post-weaning. Anorexia, immunodeficiency, male hypogonadism, vesicobullous dermatitis (perirectal, perioral, extremities), alopecia.
  • Labs: Low zinc, low alkaline phosphatase. Paneth cells show inclusion bodies.
  • Treatment: Long-term elemental zinc (1 mg/kg/day).

Newborns have a normal transient decrease in Vitamin K-dependent factors (II, VII, IX, X) by 48-72 hrs. Causes: Lack of free maternal Vit K, absence of bacterial flora. Breast milk is a poor source of Vitamin K, making breastfed infants at higher risk.

• Classification:
  • Early HDN (0-24 hrs): Severe. Risk factor: Maternal drugs (phenobarbital, phenytoin, isoniazid, warfarin, rifampin) interfering with Vit K. Bleeding sites: Cephalohematoma, subgaleal, intracranial, GI, umbilicus.
  • Late HDN (> 2 weeks): Associated with Vitamin K malabsorption (Cholestasis, biliary atresia, neonatal hepatitis, Cystic Fibrosis). Risk factors: Abetalipoprotein deficiency, Idiopathic in Asian breastfed infants. Bleeding sites: Intracranial, GI, cutaneous, ENT, injection sites.
• Diagnosis / Labs: Prolonged Prothrombin Time (PT) is the FIRST abnormal laboratory test. Activated Partial Thromboplastin Time (aPTT), fibrinogen, and Platelet count are strictly NORMAL.
• Treatment:
  • Prophylaxis: 1 mg Vitamin K Intramuscular (IM) at birth.
  • Treatment: 1-5 mg Vitamin K1 slow IV infusion (improvement in hours).
  • Severe/Life-Threatening Bleeding (CNS): Give Fresh Frozen Plasma (FFP) 10 mL/kg immediately, along with Vitamin K.
• Swallowed Blood Syndrome: Blood swallowed during delivery or from fissured maternal nipple (passed on 2nd-3rd day). Differentiate via Apt Test: Fetal hemoglobin is alkali-resistant (remains pink), whereas maternal adult Hb is promptly changed to alkaline hematin (brown) after adding alkali.

Bacterial Blood Stream Infection (BSI) in newborn (meningitis, pneumonia, pyelonephritis, gastroenteritis) with systemic signs.

• Pathogenesis / Timing:
  • Intrauterine (Transplacental): CMV, Treponema pallidum, Toxoplasma, Rubella, Parvovirus B19, Varicella.
  • Early-Onset (< 1 wk): Acquired before/during delivery (vertical mother-to-child). High risk with maternal chorioamnionitis, Premature Rupture of Membranes (PROM).
  • Late-Onset (> 1 wk): Acquired in hospital/community.
• Etiology (Pathogens):
  • Early/Meningitis: Group B Streptococcus (GBS), Escherichia coli (E. coli), Listeria monocytogenes.
  • Nosocomial (Hospital): Staphylococcal species, Gram-negative enterics (Klebsiella), Pseudomonas, Candida, RSV.
• Risk Factors: Prematurity / Low Birth Weight (LBW) is the most important factor (3-10 fold higher incidence). Others: Chorioamnionitis, immune defects, galactosemia.
• Clinical Manifestations: "Not doing well", temperature instability, poor feeding, apnea, grunting, abdominal distention, bulging fontanel, jaundice, petechiae.
• Diagnosis:
  • Blood, CSF, or Urine Culture is the Gold Standard.
  • Lumbar Puncture must be done (10-15% of sepsis have meningitis).
  • Differential Leukocyte Count (DLC): Band cells > 20%, absolute band count > 1,500/mm³.
  • Micro ESR > 15mm. C-Reactive Protein (CRP) is NOT very accurate early on.
  • Gastric aspirate showing >5 polymorphs/hpf.
• Treatment:
  • Supportive: IV NS 10ml/kg, 10% glucose (2ml/kg) for hypoglycemia, Oxygen/bag-mask, Vitamin K 1mg IM. Avoid oral feeding if very sick.
  • Antibiotics (Septicemia/Pneumonia): Ampicillin (50mg/kg 12hrly) + Gentamicin (2.5mg/kg 12hrly) for 7-10 days.
  • Meningitis: Ampicillin (100mg/kg 12hrly) + Gentamicin, or Chloramphenicol. Duration: 3 weeks.

Genetics helps in diagnosis, management, and prevention of hereditary disorders. Early detection improves outcomes.

• 1. Chromosomal Disorders: Numerical (Trisomy 21 Down, Turner 45,XO, Klinefelter), Structural (Cri du chat 5p deletion). Features: dysmorphism, developmental delay, growth failure.
• 2. Single-Gene Disorders:
  • Autosomal Dominant (AD): Marfan syndrome, Achondroplasia.
  • Autosomal Recessive (AR): Cystic fibrosis, Sickle cell disease.
  • X-linked Recessive: Duchenne muscular dystrophy, Hemophilia A.
• 3. Multifactorial Disorders: Interaction between genes + Environment. Examples: Neural tube defects, Cleft lip, Heart disease.
• 4. Mitochondrial Disorders: Maternal inheritance exclusively. Example: MELAS (affects brain, muscle, heart).

Diagnostic Tools: Cytogenetic (Karyotyping, FISH), Molecular (PCR, Sequencing), Biochemical (Enzyme assays), Prenatal (Chorionic Villus Sampling [CVS], Amniocentesis, NIPT).

Newborn Screening: Essential for Phenylketonuria (PKU), congenital hypothyroidism, galactosemia, sickle cell.

• Definition: Extra copy of chromosome 21 (total 47). Most common chromosomal abnormality in live-born infants.
• Etiology:
  • Nondisjunction (95%) - Failure of chr 21 to separate during meiosis.
  • Translocation (3-4%) - Part or all of chr 21 attached to another (often 14). Parental carrier.
  • Mosaicism (1-2%) - Mixture of normal and trisomy cells.
• Risk Factors: Advanced maternal age (>35 years), parental carrier of balanced translocation, previous child with Down syndrome.
• Physical Features: Flat facial profile, depressed nasal bridge, upward slanting palpebral fissures, epicanthic folds, protruding tongue, Single transverse palmar crease (simian crease), short broad hands/feet, Hypotonia (floppy baby), Brushfield spots (white spots on iris).
• Associated Medical Conditions (High Yield):
  • Cardiac (40-50%): Atrioventricular (AV) septal defect (most common).
  • Gastrointestinal: Duodenal atresia, Hirschsprung disease.
  • Hematologic: Increased risk of leukemia.
  • Neurological: Early onset Alzheimer disease.
  • Endocrine: Hypothyroidism. Musculoskeletal: Atlantoaxial instability (cervical spine).
• Diagnosis (Prenatal Screening):
  • First Trimester: Increased Nuchal Translucency, Increased Beta-human chorionic gonadotropin (β-hCG), Decreased Pregnancy-Associated Plasma Protein A (PAPP-A).
  • Second Trimester (Quad test): Decreased Alpha-fetoprotein (AFP), Decreased estriol, Increased β-hCG, Increased Inhibin A.
  • Definitive: Karyotyping (via CVS, amniocentesis).
• Prognosis: Life expectancy ~60 years or more. High quality of life with early intervention. No cure, requires multidisciplinary supportive care (physio, speech therapy).