Diagnosis of sideroblastic anemias

In hereditary forms, anemia of varying severity is detected in the hemogram. As a rule, anemia increases with age and is hypochromic (the color index is reduced to 0.4-0.6). Hypochromic erythrocytes are detected in smears, however, normochromic ones are also found among them; anisocytosis with a tendency to microcytosis and poikilocytosis are also determined. The number of reticulocytes is within normal limits. The number of leukocytes and platelets is within normal limits.

In lead intoxication, the hemogram reveals hypochromic anemia, hypochromic erythrocytes, target forms, anisocytosis with a tendency to microcytosis. A constant characteristic symptom of lead intoxication is basophilic granularity of erythrocytes.

In the bone marrow, hyperplasia of the erythroid germ is observed, the ratio of various forms of normocytes changes: the number of basophilic cells increases and the number of hemoglobinized oxyphilic normocytes decreases sharply. Pathognomonic is an increase (up to 70% in hereditary forms) in the number of sideroblasts (revealed with special staining), which have a characteristic morphology. Iron granules in the cell surround the nucleus in a ring - ring-shaped sideroblasts. This morphology is due to the accumulation of iron that is not used for the synthesis of heme in the cell mitochondria.

In biochemical studies, in all forms, an increase in the serum iron level by 2-4 times or more compared to the norm is noted. The transferrin saturation coefficient with iron increases to 100 %.

Diagnosis of sideroblastic anemia

The diagnosis of hereditary forms of anemia is confirmed by studying the content of porphyrins in erythrocytes. It has been established that in hereditary forms of sideroachrestic anemia, the content of erythrocyte protoporphyrin is reduced. The content of erythrocyte coproporphyrin can be both increased and decreased. Normally, the average level of erythrocyte protoporphyrin in whole blood is 18 μg%, and the upper limit in the absence of anemia is 35 μg%. To study the content of iron reserves and confirm hemosiderosis, the desferal test is used. After intramuscular administration of 500 mg of desferal, 0.6-1.2 mg of iron per day is normally excreted in the urine, and in patients with sideroblastic anemia - 5-10 mg / day.

To diagnose lead poisoning, the level of lead in venous blood is determined; the level of erythrocyte protoporphyrin in whole blood - a level above 100 μg%, as a rule, indicates the toxic effect of lead.

In chronic lead poisoning, knee radiographs show dilated and compacted calcifications in the distal femur, proximal tibia and fibula (lead lines). In acute poisoning due to ingestion of lead-containing objects, they can be detected using an anteroposterior abdominal radiograph. Knee radiographs in children under 3 years of age are difficult to interpret because lead lines can be mistaken for normal bone changes during rapid growth. The characteristic localization of bone changes is highly likely to indicate chronic lead intoxication. Lead lines usually appear when lead levels exceed 50 μg % for a long time - more than 6 weeks.

In case of moderate increase of blood lead level (35-45 μg%), if results of other tests are contradictory, test with EDTA is performed. Calcium-disodium salt of EDTA is administered at the dose of 1000 mg/m2 ^/ day or 35 mg/kg/day intramuscularly or as intravenous infusion for 1 hour. The test is considered positive if urine collected during 24 hours contains 1 μg of lead per 1 mg of administered dose of EDTA. There is no point in determining concentration of lead in urine. Only amount of lead excreted in certain period of time per administered dose of EDTA has diagnostic value. When performing the test it is necessary to ensure sufficient consumption of liquid and to collect all urine. In a general urine analysis for lead intoxication, leukocyturia, cylindruria, glucosuria or aminoaciduria can be detected (usually when the lead concentration in the blood exceeds 100 mcg%).

Examination plan for a patient with sideroachrestic anemia

1. Tests confirming the presence of sideroachrestic anemia.
   • Clinical blood test with determination of the number of reticulocytes and morphological characteristics of erythrocytes.
   • Myelogram with mandatory staining of smears with Prussian blue to detect ringed sideroblasts.
   • Biochemical blood test: iron complex, ALT, AST, FMFA, bilirubin, sugar, urea, creatinine.
2. Tests to clarify the form of sideroachrestic anemia.
   • Whole blood erythrocyte protoporphyrin level.
   • Whole blood lead level.
   • Desferal test.
   • EDTA test.
   • X-ray of the knee joints.
3. Child's life history. Pay special attention to the place of residence, home conditions, environment, appetite, nutrition, behavior, frequency of bowel movements. Specify what medications the child is taking.
4. Family history - presence of sideroblastic anemia in relatives.
5. General clinical examinations: urine and stool analysis, ECG, specialist examination, ultrasound of abdominal organs, kidneys, heart and other examinations are carried out according to individual indications.

Clinical and laboratory signs of lead poisoning

	Lung	Moderate	Heavy
Source of lead	Dust or soil	Paints	Paints (eating with perverted appetite)
Symptoms	None	Decreased appetite and behavioral disorders	Abdominal pain, irritability, drowsiness, fever, hepatosplenomegaly, ataxia, seizures, increased intracranial pressure, coma, signs of iron deficiency
Predisposing factors	Iron deficiency	Iron deficiency	Iron deficiency
Consequences	Impaired cognitive abilities	Behavioral disorders, cognitive impairment	Persistent neurological impairment
Whole blood lead level, mcg%	25-49	49-70	>70
Erythrocyte protoporphyrin level, mcg %	35-125	125-250	>250
Transferrin iron saturation coefficient	<16	<16	<16
Serum ferritin level, ng/ml	<40	<20	< 10
EDTA test: lead content in daily urine per 1 mg EDTA		1	>1
Urine analysis			Aminoaciduria, glucozuria
X-rays of the knee joints, kidneys, bladder	No changes	Changes in the knee joints	Changes in the knee joints, kidneys, bladder
CT scan of the head			Signs of increased intracranial pressure
Speed of excitation propagation along the nerve			Enlarged
General analysis and blood smear		Mild anemia	Anemia, basophilic granularity of erythrocytes

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