- Causes of stridor In pediatrics.

Causes of stridor according to site of obstruction.

-Nose and pharynx: (by laryngeal compression)

• Lingual thyroid or thyroglossal cyst 
• Macroglossia(Beckwith-Wiedemann syndrome, hypothyroidism, Pompe disease, trisomy 21, hemangioma).
• Micrognathia (Pierre Robin syndrome, Treacher Collins syndrome,DiGeorge syndrome)
• Hypertrophic tonsils/adenoids
• Retropharyngeal or peritonsillar abscess / hematoma
• Tongue teratoma or dermoid 
• Masses: e.g. cystic hygroma or other malformation

-Larynx:
Not acute:

• Laryngomalacia
• Congenital subglottic stenosis
• Vocal cord paralysis
• Laryngeal atresia/web 
• Congenital Subglottic hemangioma
• Vascular ring compression syndrome.
• Laryngocele/cyst
• Laryngeal papillomas 
• GERD

- Infant girl with whooping cough (Video)

Infant girl with whooping cough

Mother holding infant girl in Intensive Care Unit. The baby has pertussis (whooping cough) and is coughing severely.

- Baby with viral croup (video).

2 years old female presenting with barking cough, stridor

The child have:

• stridor at rest 
• Subcostal and suprasternal retraction 

As classified by Westley score  minimally she has Moderate croup

- Pathogenesis of Acute Bronchiolitis.

Pathogenesis of Acute Bronchiolitis. 

RSV initially multiplies in the epithelium of the nasopharynx.
It then forms a syncytium and invades nearby cells.
 Hence, progression within few days of illness from an upper respiratory infection to a lower respiratory tract involvement is from cell to cell rather than hematogenous, extra-cellular fluid or any other route.
 The virus mainly multiplies within the bronchial epithelium and the alveolar macrophages.

 It finally results in:
o Destruction of the bronchiolar lining epithelium and loss of ciliated epithelial cells.
o Peribronchial infiltration of white blood cells.
o oedema of the submucosa and adventitia.
o ↑ Secretion
o Plugs of sloughed, necrotic epithelium and fibrin in the airways cause significant small airway obstruction (bronchospasm) resulting in hyperinflation, obstructive emphysema, atelectasis and ventilation/perfusion mismatch leading to hypoxemia.

N.b: Bronchial muscles are spared in bronchiolitis.

- Hospital and PICU admission criteria in cases of acute bronchiolitis.

Hospital and PICU admission criteria in cases of acute bronchiolitis.

Hospital Admission Criteria:

• Hypoxemia <90% on room air
• Dehydration with inability to maintain hydration
• Major comorbidity
• Need to rule out alternative diagnosis
• heart rate >180 bpm
• Moderate to Severe distress
• Inability to care for child at home.
• Strongly consider in infants with high-risk criteria:

- LBW
- age <6 wk,
- Prematurity
- Cardiac (Pulmonary hypertension,heart failure or cyanotic heart disease) .
- Pulmonary disease (BPD, cystic fibrosis or congenital anomalies of airway)
- Immunodeficiency
- neuromuscular disease

Critical care admission criteria:

• Recurrent apneas
• Concern regarding impending respiratory failure, increasing oxygen requirements
• High risk criteria…

- Henoch-Schönlein Purpura (Anaphylctoid purpura)

Henoch-Schönlein Purpura (Anaphylctoid purpura)

Immune complex mediated disease contain IgA within capillaries of skin, GI and renal involvement.
Incidence:

• HSP is the commonest generalized vasculitis of childhood.
• HSP is the commonest cause of non-thrombocytopenic purpura in children.
• Can occur at any age but peaking at 3–10 years of age.
• Male : female = 2:1
• Peaks during the winter months.

Etiology: the cause is unknown.
- It is postulated that genetic predisposition and antigen exposure increase circulating IgA levels and disrupt IgG synthesis.
-The IgA and IgG interact to produce complexes that activate complement and are deposited in affected organs, precipitating an inflammatory response with vasculitis.
- Antigen may be:

• Infections (e.g. Group A ß hemolytic streptococci or ohers)
•  Insect bites
• Drugs or food allergy.

Pathology and pathogenesis:

• IgA-mediated vasculitis of small blood vessels with IgA deposits seen in these vessels, primarily those of the skin and intestine.
• Deposition of polymeric immunoglobulin A (IgA) in glomeruli. 
• IgA deposits are present by immunofluorescence,
•  Broad spectrum of glomerular lesions that can range from mild proliferation to necrotic and crescentic changes can be seen

- Alport Syndrome (Hereditary nephritis).

Alport Syndrome (Hereditary nephritis)

AS, or hereditary nephritis, is a genetically heterogeneous disease caused by mutations in the genes coding for type IV collagen, a major component of basement membranes which is present in kidney, ear, and ocular lens.

GENETICS

• The most common form of hereditary nephritis.
• Approximately 85% of patients have X-linked inheritance caused by a mutation in the COL4A5 gene encoding the α5 chain of type IV collagen.
• Autosomal recessive forms of AS (10%)are caused by mutations in the COL4A3 and COL4A4 genes on chromosome 2 encoding the α3 and α4 chains, respectively, of type IV collagen.
• An autosomal dominant form of AS linked to the COL4A3-COL4A4 gene locus occurs in 5% of cases.

PATHOLOGY
- Light microscopy:

• Kidney biopsy specimens during the 1st decade of life show few changes
• Later, the glomeruli may develop mesangial proliferation and capillary wall thickening, leading to progressive glomerular sclerosis. Tubular atrophy, interstitial inflammation and fibrosis, and lipid-containing tubular or interstitial cells, called foam cells, develop as the disease progresses.