28.3 Pediatric Hematology, Allergy & Immunology: Normal Hemogram and Immunoglobulins by Age, Anemias (Iron Deficiency, Thalassemia, G6PD, Spherocytosis, Aplastic), Bleeding Disorders (ITP, Hemophilia, vWD, DIC, Vitamin K), IgA Vasculitis, Rashes and Drug Reactions, Asthma, Allergic Rhinitis and Primary Immunodeficiencies

Why this area matters

The TOS heme-immunology competencies are to:

• know normal hemogram and immunoglobulin values and recognize abnormal ones;
• classify anemias by morphology;
• analyze the burden of these diseases;
• prioritize tests;
• manage the conditions, promote health and refer appropriately.

Iron deficiency anemia is common in Filipino infants, toddlers, adolescent girls and pregnant women. Thalassemia and G6PD deficiency are common inherited disorders in the Philippines. Asthma and allergic diseases are leading chronic illnesses of childhood.

Normal values by age

• Newborn: hemoglobin is high (about 14 to 20 g/dL) with high MCV and mostly fetal hemoglobin.
• Physiologic anemia of infancy: hemoglobin falls to its lowest point at 8 to 12 weeks (about 9 to 11 g/dL in term infants). The fall is earlier and deeper in preterm infants (anemia of prematurity).
• Childhood: MCV rises gradually through childhood.
• White cells: lymphocytes predominate from about 1 week to 4 to 5 years, then neutrophils predominate.
• Immunoglobulins:
  • IgG at birth is maternal and falls to a nadir at 3 to 6 months, then the infant's own IgG rises;
  • IgM rises first;
  • IgA reaches adult levels last, in adolescence.
  • A raised IgM in cord blood suggests congenital infection.

Anemias

• Thalassemia major (beta):
  • severe anemia from 6 to 12 months;
  • hepatosplenomegaly;
  • frontal bossing and maxillary overgrowth ("chipmunk facies") from marrow expansion;
  • "hair-on-end" skull X-ray;
  • treated with regular transfusions with iron chelation (deferoxamine, deferasirox) and stem cell transplant.
  • Carrier screening and counseling prevent new cases.
• G6PD deficiency:
  • X-linked; common in the Philippines and detected by newborn screening;
  • acute hemolysis after oxidant triggers: infections, naphthalene mothballs, fava beans, some drugs (primaquine, sulfonamides, nitrofurantoin, high-dose aspirin);
  • Heinz bodies and bite cells;
  • neonatal jaundice;
  • prevention is avoiding the triggers.
• Hereditary spherocytosis: autosomal dominant, with spherocytes, increased osmotic fragility, splenomegaly, gallstones and aplastic crises with parvovirus. Treated with folate and splenectomy (after vaccination) in severe cases.
• Sickle cell disease is uncommon in Filipinos but tested: vaso-occlusive crises, dactylitis, splenic sequestration, functional asplenia and Salmonella osteomyelitis.
• Aplastic anemia: pancytopenia with an empty marrow. Fanconi anemia adds short stature, absent thumbs or radii and café-au-lait spots.

Bleeding disorders and vascular defects

• ITP management:
  • most children recover within weeks to months;
  • observe if bleeding is only cutaneous, whatever the count;
  • give IVIG or corticosteroids for mucosal or significant bleeding;
  • avoid aspirin, NSAIDs and IM injections;
  • before giving steroids, check the smear to exclude leukemia.
• Hemophilia: replace the missing factor. Desmopressin helps mild hemophilia A and vWD. Avoid IM injections and NSAIDs.
• Vascular defect: IgA vasculitis (Henoch-Schonlein purpura):
  • palpable purpura on the buttocks and legs with normal platelets;
  • arthritis;
  • colicky abdominal pain (intussusception risk);
  • nephritis.

Rashes and drug reactions

• Urticaria and angioedema:
  • hives from infections, foods, drugs or insect stings;
  • angioedema of the lips and eyelids;
  • give antihistamines, and IM epinephrine if there is airway compromise or anaphylaxis;
  • recurrent angioedema without urticaria suggests hereditary angioedema (C1 inhibitor deficiency).
• Atopic dermatitis:
  • itchy eczema on the face and extensor surfaces in infants and flexural areas in older children;
  • part of the atopic march with asthma and allergic rhinitis;
  • managed with emollients, bathing care, topical corticosteroids or calcineurin inhibitors, and treatment of infection (S. aureus, eczema herpeticum).
• Contact dermatitis: irritant (diaper dermatitis) or allergic (nickel, plants). It is limited to the area of contact.
• Stevens-Johnson syndrome and toxic epidermal necrolysis:
  • severe mucocutaneous reactions, usually 1 to 3 weeks after starting a drug: anticonvulsants (carbamazepine, phenytoin, lamotrigine, phenobarbital), sulfonamides, allopurinol, nevirapine, NSAIDs; Mycoplasma in children;
  • fever, target lesions, mucosal erosions (eyes, mouth, genitals) and skin detachment (under 10% in SJS, over 30% in TEN);
  • stop the drug at once, give burn-unit-type care and eye care.

Asthma and allergic rhinitis

• Asthma:
  • recurrent wheeze, cough (often at night or with exercise), breathlessness and chest tightness that are reversible;
  • triggers are viral infections, allergens (dust mites, cockroaches), smoke and exercise;
  • control is assessed by symptoms;
  • inhaled corticosteroids are the controller;
  • treatment steps up as needed.
• Acute asthma exacerbation:
  • salbutamol by spacer or nebulizer, repeated three times in the first hour;
  • oral or IV corticosteroids;
  • oxygen to keep saturation at 94% or more;
  • ipratropium in severe attacks;
  • IV magnesium sulfate for severe attacks not responding;
  • a silent chest, cyanosis, exhaustion, confusion or a normal or rising PaCO2 signals life-threatening asthma.
  • Inhaler technique and a written action plan are essential.
• Allergic rhinitis: sneezing, itching, clear rhinorrhea, "allergic shiners" and a nasal crease from the "allergic salute". Treat with allergen avoidance, intranasal corticosteroids and non-sedating antihistamines.

Primary immunodeficiencies

• Warning signs include:
  • recurrent ear or sinus infections;
  • two or more pneumonias a year;
  • failure to thrive;
  • recurrent deep abscesses;
  • persistent thrush;
  • the need for IV antibiotics;
  • a family history.