pediatric

1. Sickle cell anemia
A type of chronic hemolytic anemia caused by the presence of abnormal
hemoglobin called Hb S.
ETIOLOGY : The disease is transmitted as autosomal recessive.
- Sickle cell anemia occurs in patients who are homozygous for sickle
cell gene. In this case 90 % of the Hb F , and Hb A2 but no HbA .
- If the person is heterozygous for the gene (as the parents of infants
with sickle cell anemia ), he is said to have sickle cell trait. here,the
RBCs contain a mixture of Hb A and HbS (25-45% as Hb S) and sickling
does not occur except if the individual is exposed to severe hypoxia
resulting from shock or flying in high atitudes in non pressurized
aircraft. No anemia is present under normal conditions.

2. Pathogenesis:
Hb S has the same structure as Hb A ,but valine replaces
glutamic acid in position number 6 of beta polypeptide chain.
This minor change leads to an important change in the
physical characters of Hb and that is : when it is exposed to
hypoxia ,dehydration , acidosis and increase or decrease in
body temperature  polymerization in the shape of RBCs
which become sickle shape , rigid , not compressible and
thus unable to pass through very small blood vessels, instead
they become entangled and obstruct the blood vessel and
finally destroyed.

3. Pathology: the manifestation of this disease are due
to :
1.Chronic hemolytic anemia.
2.Interference of blood supply of various tissues .
infarcts may occur in many organs as the spleen ,
GIT , kidneys, heart and brain. Hemosiderosis may
occur due to repeated blood transfusion.

4. Clinical manifestations:
The manifestations of the disease do not appear in
the first 3-4 months as Hb F protects against
sickling. The manifestations are those of chronic
hemolytic anemia + crises. Manifestation of
anemia are usually less marked than thalassemia
major . the crises are of 4 types:

5. 1. Vaso-oclusive (painful or thrombotic) crises:
- The most important type . they are caused by occlusion of
blood capillaries with distal ischemia and infaction.
Thrombotic criese occur spontenously or precipitated by
infection. Clinically , it presents as dactylitis , limb pains,
chest pains or abdominal pains ( due to mesenteric vein
thrombosis),hemiplegia(due to thrombosis of cerebral
blood vessels) , pulmonary infaction, hematuria , …..etc.
- The spleen is usually enlarged in early childhood (as cases
of hemolytic anemias )but later decreases in size due to
repeated thrombi which leads to splenic infarctions and
shrinkage (self splenectomy).

6. 2. Aplastic crises :(transient erythroblastopenia)
Sudden attacks of bone marrow aplasia (affecting
mainly RBCs production) last for 10-14 days and
recover spontaneously . it is usually associated
with infection by parvovirus. c/p acute onset of
severe anemia +reticulocytes.

7. 3. Hyperhemolytic crises:
Uncommon but may be precipitated by infection.
They occur mainly in children with combined
sickle cell disease _G6PD deficiency . the patient
presents as a case of acute hemolytic anemia
(severe pallor +jaundice +red or brown urine).

8. 4. Splenic sequestration crises:
Large amount of blood become sequestrated in the
spleen  sudden huge splenomegaly and circulatory
collapse (rapid pulse and hypotension or shock).
It is etiology is unknown.
Due to to splenic dysfunction , patients with sickle cell
anemia are predisposed to salmonella infection(as
osteomyelitis) and pneumococcal septicemia ,
H.influenza , staphylococcus aureus and mycoplasma
pneumonia but resistant to falciparum malaria.

9. Laboratory findings:
1. Complete blood picture:
- Normochromic normocytic anemia, Reticulocytosis (except
in aplastic crises )and increased nucleated red cells.
- Target cells ,sickle cells are seen in blood film,(picture)
- Leukocytosis during crises and thrombocytosis.
2. Unconjugated hyperbilirubinemia.
3. Sickling test is positive : the RBCs are examined under
conditions of low oxygen tension sickling.
4. Hb electrophoresis: in sickle cell anemia Hb S and Hb A2
and Hb F but no Hb A.
IN SICkLE CELL TRAIT: Hb A , Hb S and Hb A2.

11. Treatment:
1. Packed red cell transfusion in severe anemia and aplastic crises.
2. Management of vaso-oclusive crises:
- Bed rest, good hydration (oral or parental)
- Analgesics as paracetamol, ibuprofen, codeine or morphine.
- Partial exchange transfusion for refractory cases
- Hydroxyurea may be given to increase Hb F and so decrease the
number and severity of attacks
3. Protection against and proper treatment of infection:
- Pneumococcal , H.influenzae , Hepatitis B and influenza virus vaccines
should be given.
- Long acting penicillin from 3-4 months of age till the age of 6
years(pneumococcal vaccines does not protect against all strains of
pneumococci).