Pediatrics

Question 1

Fifth disease (erythema infectiosum)

Accepted Answer

Epidemiology:- Peak incidence: 5-15 years- Pathogen: Human parvovirus B19 Pathophysiology: Parvovirus B19 binds to the P antigen (globoside) on erythroid progenitor cells → cellular invasion → viral DNA enters the nucleus of erythroid cells → viral DNA replication → cytotoxicity → clinical manifestations + transient cessation of erythropoiesis Clinical features:- Mild cold‑like symptoms- Exanthem: 2-5 days following the onset of cold‑like symptoms→ Initial diffuse redness of the face with perioral sparing (slapped‑cheek rash)- Spread of exanthem to the extremities and trunk→ Initially confluent and maculopapular; adopts a lace‑like, reticular appearance over time as it clears.→ Associated with mild pruritus (in ∼ 50% of cases)- Fades after ∼ 7-10 days; may be recurrent over several weeks (becoming more pronounced after exposure to sunlight or heat) Parvovirus B19-associated arthritis:- Epidemiology: affects < 10% of children and up to 60% of adults (♀ > ♂) infected with parvovirus B19- Clinical findings: Arthralgia with symmetrical, nondestructive polyarthritis, particularly in the joints of the fingers, hand, knee, and ankle Diagnostics:- Immunocompetent children: Clinical- Immunocompetent adults: Antibody testing Treatment: - Not necessary in most cases, as the disease is often self-limiting- Analgesics and nonsteroidal anti‑inflammatory drugs (NSAIDs)- Short course of low‑dose prednisone for parvovirus B19‑associated arthritis Complications:- Transient aplastic crisis in patients with chronic hemolytic diseases- Chronic pure red cell aplasia in immunocompromised patients- Hydrops fetalis, fetal death, and miscarriage

Question 2

Retropharyngeal abscess

Accepted Answer

Epidemiology:- Most common in children < 5 years of age- ♂ > ♀ Etiology:- Pathogen: Streptococci (viridans Streptococci, S. pneumoniae), Staphylococci (including MRSA), Haemophilus influenzae, oral anaerobes (Peptostreptococci, Bacteroides species), often in a polymicrobial environment Clinical features:- Features of tonsillitis and trismus (minimal)- Neck asymmetry with unilateral swelling of the posterior pharyngeal wall (possible fluctuance) → inability to extend neck- Torticollis- Muffled voice- Anterior cervical lymphadenopathy- Respiratory distress- Infants may also present with lethargy, cough, poor intake, rhinorrhea, and agitation. Diagnosis:- Contrast-enhanced CT: shows hypodense lesion in retropharyngeal space, soft-tissue swelling, peripheral ring enhancement, mass effectInitial step if in no signs of respiratory compromise- Gram stain and culture of aspirated abscess fluid and blood to identify causative pathogen Treatment:- Airway management- IV broad-spectrum antibiotics: empiric options include ampicillin-sulbactam or clindamycin.- Needle aspiration or incision and drainage of abscess (surgical drainage) should be performed immediately in patients with a compromised airway or other life-threatening complications Complications:- Airway obstruction- Spread of infection to carotid sheath (internal carotid artery erosion, jugular vein thrombophlebitis) and then mediastinum (acute necrotizing mediastinitis with widened mediastinum on chest x-ray) - Infection can spread and enter the skull base (epidural abscess) or the posterior mediastinum (pericarditis)- Aspiration pneumonia- Atlantoaxial dislocation- Bacteremia and sepsis

Question 3

Peritonsillar abscess

Accepted Answer

Epidemiology:- Most common deep neck infection- Most common in adolescents and young adults Etiology:- Pathogens: Streptococcus pyogenes (most common), Streptococcus anginosus, viridans streptococci, Staphylococcus aureus, and Haemophilus species, often in a polymicrobial environment - Acute bacterial tonsillitis (see acute tonsillitis) Clinical features:- Features of tonsillitis: fever, malaise, severe sore throat, dysphagia, and odynophagia- “Hot potato” voice (muffled speech), drooling, or halitosis- Trismus- Uvula shifted to the contralateral side, with inferior and medial displacement of tonsil- Unilateral fluctuant, swollen, erythematous tonsil with exudates (ipsilateral bulging of the palatine arch) - Ipsilateral cervical lymphadenopathy (and neck swelling) Diagnosis: Usually a clinical diagnosis- Gram stain and culture of aspirated abscess fluid, and throat culture to identify causative pathogen- Contrast-enhanced CT if there is a clinical suspicion of other diagnoses or complications Treatment:- Airway management- IV antibiotics with good gram-positive and anaerobic coverage: empiric clindamycin or ampicillin-sulbactam - Incision and drainage or needle aspiration (surgical drainage): risk of airway obstruction, complications, or immunodeficiency. - Tonsillectomy indicated if: Unresponsive to drainage and antibiotics, recurrent tonsillitis or peritonsillar abscess

Question 4

Bacterial tracheitis

Accepted Answer

DD: Croup Epidemiology:- Children ages 5-7 (older than croup) Clinical features:- More ill-appearing- Don't respond to racemic epinephrine Diagnostics:- X-ray: Subglottic narrowing- Tracheal culture Treatment: Antibiotics

Question 5

Apt test (Alkali denaturation test)

Accepted Answer

A hematologic test used to differentiate neonatal or fetal blood from maternal blood by exposing blood to sodium hydroxide. Fetal hemoglobin's resistance to alkali denaturation allows it to remain intact, and it appears pinkish under microscopy (indicating a positive test), while adult hemoglobin gives off a light-brownish color due to denaturation. Indications:- Newborn gastrointestinal (stool, vomiting) or pulmonary bleeding- Antepartum bleeding of unknown origin (e.g., vasa previa).

Question 6

Strabismus

Accepted Answer

Abnormal findings:- Constant strabismus at any age- Eye deviation after 4 months of age- Asymmetric corneal light reflexes- Asymmetric intensity of red reflexes- Deviation on cover test- Torticollis or head tilt Treatment:- Penalization therapy: Cyclopegic drops to blur normal eye- Occlusion therapy: Patch normal eye- Prescription eyeglasses- Surgery at 6 months Complications: Amblyopia, diplopia

Question 7

Chlamydial conjunctivitis

Accepted Answer

Pathogen: C. trachomatis Onset after birth: 5-14 days Clinical features:- Watery/mucopurulent ocular discharge- Mild eyelid swelling Diagnosis: Cultures and gram stain (on blood, chocolate agar, and conjunctival scrapings) or PCR Treatment:- Newborns: Oral erythromycin- Mother and at-risk contacts: PO doxycycline (for 1 week)

Question 8

Scarlet fever

Accepted Answer

Etiology: Streptococcus pyogenes Epidemiology:- Peak incidence: 5-15 years- Occurs in < 10% of streptococcal causes of tonsillopharyngitis Clinical features:- Fever & pharyngitis- Tonsillar erythema & exudates- Strawberry tongue- Tender anterior cervical nodes- Sandpaper rash- Pastia's lines→ Linear, petechial appearance→ Most pronounced in the groin, underarm, and elbow creases (i.e., flexural areas)- Location: Begins on neck, disemminates to trunk and extremities Diagnosis:- Rapid streptococcal antigen test- Throat culture Treatment: Penicillin (eg, amoxicillin)- In patients allergic to penicillin: macrolides

Question 9

Rickets

Accepted Answer

Risk factors:- Exclusive breastfeeding- Inadequate sun exposure- Increased skin pigmentation- Maternal vitamin D deficiency Clinical features:- Craniotabes ("ping-pong ball" skull): softening of the occipital bones- Varus/valgus deformities of the knees- Widening of wrists- Delayed fontanel closure- Frontal bossing- Hypertrophy of costochondral joints ("rachitic rosary")- Femoral & tibial bowing once weight-bearing Evaluation:- Serum calcium ↓, phophorus ↓, alkaline phosphatase ↑; PTH ↑, 25-hydroxyvitamin D; 1,25-dihydroxyvitamin D- Radiography Management: Vitamin D & calcium supplementation

Question 10

Preseptal vs orbital cellulitis

Accepted Answer

Preseptal cellulitis:- Eyelid erythema & swelling- Chemosis- Treatment: Oral antibiotics Orbital cellulitis:- Symptoms of preseptal cellulitisPLUS- Pain with extraocular movements, proptosis &/or ophthalmoplegia with diplopia- Treatment: IV antibiotics ± surgery

Question 11

Innocent murmur

Accepted Answer

Never diastolic 1/6 or 2/6

Question 12

Down syndrome

Accepted Answer

The most common autosomal chromosome aberration, occurring in approximately 1:700 livebirths. Eyes:- Upward slanting of the eyelids, epicanthus, hypertelorism- Brushfield spots (aggregation of connective tissue in periphery of iris, visible as white or grayish-brown spots)- Refractive errors (e.g., short-sightedness, astigmatism), strabismus- Cataracts (congenital, infantile, or juvenile)Mouth:- Small oral cavity, large tongue- High arched palate- Abnormal teeth Further features:- Brachycephaly (Short skull due to premature closure of the coronal suture)- Hypoplastic nasal bones, broad and flat nasal bridge- Ear anomalies (small, round low-set ears, adherent earlobes)Extremities:- Single transverse palmar crease: crease across the palm, which runs along the metacarpophalangeal joints perpendicular to the fingers- Sandal gap: large space between the first and second toe - Clinodactyly, camptodactyly, brachydactyly- Soft tissue: connective tissue deficiency → ↑ increased risk of umbilical and inguinal hernias; marked hyperextension of joints may occur- Atlantoaxial instabilityHeart: congenital heart defects in ∼ 50% of cases – atrioventricular septal defect (∼ 40%), ventricular septal defect (∼ 30%), atrial septal defects (∼ 15%), tetralogy of Fallot (∼ 5%)Gastrointestinal tract: duodenal atresia/stenosis, annular pancreas, imperforate anus, enlargement of the colon, rectal prolapse, Hirschsprung diseaseUrogenital system: hypogonadism, cryptorchidism, decreased fertility in menFurther features: hypothyroidism, celiac disease, sleep apnea, hearing loss due to recurrent otitis media, ↑ risk of leukemia (acute lymphoblastic leukemia, acute myeloid leukemia), ↑ risk of Alzheimer disease (75% of individuals affected by age of 40 years), ↑ risk of developing epilepsy

Question 13

Congenital and newborn listeriosis

Accepted Answer

Pathogen: Listeria monocytogenes Transmission: vertical transmission during pregnancy or delivery Clinical features:- ↑ Risk of premature birth and spontaneous abortion- Early-onset syndrome: granulomatosis infantiseptica→ Severe systemic infection characterized by disseminated abscesses, which may develop in any organ system→ Most common findings are respiratory distress syndrome and skin lesions→ May be associated with signs of meningitis- Transmission during birth, postnatally via contact with the mother or environment→ Late-onset syndrome (5 days to 3 weeks after birth): Listeria meningitis/encephalitis Diagnosis: culture from blood or CSF samples (pleocytosis) Treatment: IV ampicillin and gentamicin for both pregnant women and newborns Prevention:- Avoiding soft cheeses- Food and water safety measures- Nationally notifiable condition

Question 14

Phenylketonuria

Accepted Answer

A congenital disorder characterized by accumulation of phenylalanine Etiology: mutations in the PAH gene Inheritance: autosomal recessive Pathophysiology: Accumulation of phenylalanine due to impaired conversion to tyrosine Clinical features:- Symptoms may manifest within the first few months of life.- Psychomotor delay (starting as early as 4-6 months of age) - Seizures - Blue eyes; light, pale hair - Eczema- Musty odor - Maternal PKU: in pregnant women with PKU who do not follow proper diet during pregnancy; infant is at risk of microcephaly, growth restriction, facial dysmorphisms, congenital heart defects, intellectual disability Diagnostics:- Newborn screening: direct measurement of serum phenylalanine levels on the 2nd-3rd day after birth - If screening test is positive: oral tetrahydrobiopterin loading test → Performed to differentiate between PKU and tetrahydrobiopterin deficiency - ↑ Phenylketones in urine: phenylacetate, phenyllactate, phenylpyruvate Treatment:- Low phenylalanine and high tyrosine diet - BH4 deficiency: supplementation of tetrahydrobiopterinPatients with PKU should be advised to avoid aspartame, an artificial sweetener that contains phenylalanine!

Question 15

Traumatic brain injury

Accepted Answer

Diagnosis: cranial CT without contrast- Identify patients with significant TBI but avoid unnecessary radiographic testing- CT recommended for signs of skull fractures, ↑ ICP, major neurologic symptoms (e.g., impaired consciousness, seizures), suspected child abuse- Consider CT: if less severe symptoms (e.g., changes in behavior, self-limited vomiting) are present. Management:- Inpatient observation indications→ Skull fracture > 3 mm separation or depressed→ Evidence of traumatic brain injury on imaging (e.g.., intracranial hemorrhage)→ Signs of ↑ ICP (e.g., headache, altered mental status)→ Suspected physical abuse- Release and at-home observation for 24 hours→ Patients without neurological deficits and non-depressed linear skullfracture < 3 mm separation→ Requires a caregiver who can reliably recognize new clinical neurological deficits and return the patient to the hospital if such manifestations arise

Question 16

Urinary tract infection

Accepted Answer

Diagnosis:- Urinalysis and urine culture- Criteria for diagnosis includes both a positive urinalysis (pyuriaand/or bacteriuria) and urine culture (> 50,000 CFU/mL).- A clean-catch urine sample may be obtained if the child is toilet trained. If not trained, a straight catheterization is necessary.- Indicated in patients with suspected UTI that fulfill one of the following criteria:→ Females and uncircumcised males of < 24 months of age with one of the following risk factors: either fever of unknown source or of duration > 24 hours, history of UTI, ill appearance, suprapubic tenderness, or nonblack race→ Circumcised boys < 24 months of age with at least two of the above risk factors→ Children older than 24 months with a suspected UTI based on urinary symptoms→ Any febrile infant or child with an abnormal urinary tract or family history of urinary tract disease- Renal and bladder ultrasound→ Indications: Infants aged 2-24 months with a febrile UTI- Voiding cystourethrography (VCUG)→ Indications: abnormal ultrasound (hydronephrosis, obstruction, scarring, or masses), abnormal voiding pattern, or recurrent UTI Treatment:- Treatment principles in children are similar to adults- Empiric therapy: second- or third-generation cephalosporin (cefdinir, cefixime, cefpodoxime)

Question 17

Laryngeal papillomatosis

Accepted Answer

Etiology:- Human papillomavirus (HPV) subtypes 6 and 11- Acquired via vertical transmission prior to delivery Clinical features:- Hoarseness Diagnostics:- Laryngoscopy: Finger-shaped, warty, or grapelike; dark-red punctate areas corresponding to blood vessels Treatment:- Surgical debridement

Question 18

Contraindications for vaccination

Accepted Answer

- Severe, acute illness: e.g., infection with fever > 38.5°C (> 101.3°F)- Previous adverse reaction related to a vaccination: e.g. anaphylaxis- Severe allergies to components of a vaccine: e.g., egg white in some live vaccines (e.g., yellow fever)- Live vaccinations are not recommended for→ Pregnant individuals→ Immunodeficient individuals Special contraindications:- Rotavirus vaccine: severe combined immunodeficiency (SCID), history of intussusception, uncorrected GI tract malformation (e.g., Meckel's diverticulum)- Hepatitis B: infant weighing less than 2 kg- Tetanus: Guillain-Barré syndrome within 6 weeks after a previous dose of tetanus toxoid-containing vaccine- Pertussis-containing vaccines: known anaphylactic reactions, encephalopathy within 7 days following previous vaccination, progressive or unstable neurologic disorder (e.g., coma, uncontrolled seizures, or progressive encephalopathy)

USMLE Step 2 (Fach) / Pediatrics (Lektion)