Causes of SCID
Causes of SCID (Diseases Database):
The follow list shows some of the possible medical causes of SCID
that are listed by the Diseases Database:
Source: Diseases Database
SCID Causes: Book Excerpts
What causes SCID?
Causes: SCID:
Genes and Disease by the National Center for Biotechnology (Excerpt)
All forms of SCID are inherited.
(Source: Genes and Disease by the National Center for Biotechnology)
Primary Immune Deficiency, NIAID Fact Sheet: NIAID (Excerpt)
A number of genetic abnormalities can
cause SCID. The two most common forms are linked to the X
chromosome. Patients with abnormalities on this chromosome either 1)
lack an enzyme called adenosine deaminase (ADA), or 2) lack the
ability to produce IL-2 receptor gamma chain, a molecule that T
cells need to communicate with B cells. (Source: excerpt from Primary Immune Deficiency, NIAID Fact Sheet: NIAID)
Related information on causes of SCID:
As with all medical conditions,
there may be many causal factors.
Further relevant information on causes of SCID may be found in:
Causes of SCID: Online Medical Books
16 MEDICAL BOOKS ONLINE!
Review excerpts from medical books online, free, without registration,
for more information about the causes of SCID.
Common variable immunodeficiency:
Causes
(Professional Guide to Diseases (Eighth Edition))
The cause of common variable immunodeficiency is unknown. Most patients have a normal circulating B-cell count but defective synthesis or release of immunoglobulins. Many also exhibit progressive deterioration of T-cell (cell-mediated) immunity revealed by delayed hypersensitivity skin testing.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Severe combined immunodeficiency disease:
Causes and incidence
(Professional Guide to Diseases (Eighth Edition))
SCID is usually transmitted as an autosomal recessive trait, although it may be X-linked. In most cases, the genetic defect seems associated with failure of the stem cell to differentiate into T and B lymphocytes. Many molecular defects such as mutation of the kinase ZAP-70 can cause SCID. X-linked SCID is due to a mutation of a subunit of the interleukin (IL)-2, IL-4, and IL-7 receptors. Less commonly, it results from an enzyme deficiency.
SCID affects more males than females. Its estimated incidence is 1 in every 100,000 to 500,000 births. Most untreated patients die from infection within 1 year of birth.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Common variable immunodeficiency:
Causes
(Handbook of Diseases)
Exactly what causes common variable immunodeficiency is unknown. Most patients have a normal circulating B-cell count but defective synthesis or release of immunoglobulins. Many also exhibit progressive deterioration of T-cell (cell-mediated) immunity, which is revealed by delayed hypersensitivity skin testing.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Severe combined immunodeficiency disease:
Causes
(Handbook of Diseases)
SCID is usually transmitted as an autosomal recessive trait, although it may be X-linked. In most cases, the genetic defect seems associated with failure of the stem cell to differentiate into T and B lymphocytes.
Many molecular defects, such as mutation of the kinase ZAP-70, can cause SCID. X-linked SCID results from a mutation of a subunit of the interleukin-2 (IL-2), IL-4, and IL-7 receptors. Less commonly, it results from an enzyme deficiency.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Cough - Case 4-2: 7-Week-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
The causes of a chronic cough in an infant are diverse, but the most common
causes are viral infections. In infants with a history of conjunctivitis,
C. trachomatis should be considered. B. pertussis can occur in infants and produce a chronic cough. Most often, infants are unable
to generate the force necessary for the classic
“whoop.” Certainly, other bacterial pneumonias should be considered with the lobar
infiltrate noted on chest roentgenogram in this case. Finally, GER must always
be considered a common cause for cough in infancy. Other, less common causes of
cough in this age group include congenital malformations including
tracheoesophageal fistulas, tracheobronchomalacia, vascular rings, lobar
emphysema, bronchogenic cyst, pulmonary sequestration, laryngeal cleft, and
airway hemangiomas.
Congestive heart failure should always be considered, with common etiologies in
infancy being volume overload (patent ductus arteriosus, truncus arteriosus,
ventricular septal defect, common atrioventricular canal, total anomalous
pulmonary venous return), myocardial dysfunction (myocarditis, Kawasaki
syndrome, anomalous left coronary artery), arrhythmias (supraventricular
tachycardia), pressure overload (coarctation of the aorta, aortic stenosis),
and secondary causes (hypertension, sepsis).
The features of this case that prompted additional evaluation were cardiomegaly
and increased vascular markings noted on the chest roentgenogram, presence of a
heart murmur, and biventricular hypertrophy seen on the ECG.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Cough - Case 4-6: 4-Month-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
A cough in infancy is most likely related to an infectious process, with viral
processes the leading causes. Respiratory syncytial virus is a common cause of
cough. However, other infectious etiologies should always be considered. Even
with good adherence to vaccine regimens, bacterial infections such as
B. pertussis are possible in infants. M. pneumoniae infections also occur rarely in infants.
Reactive airways disease, most often secondary to viral infection, is also a
common cause of cough in infancy. GER should be considered as well, even if
gastrointestinal symptoms are few.
Less common causes for cough in infancy include congenital malformations such as
tracheoesophageal fistula, tracheobronchomalacia, vascular rings, lobar
emphysema, bronchogenic cysts, pulmonary sequestration, laryngeal cleft, and
cystic adenomatoid malformation. Furthermore, one should attempt to elicit a
history for any possible swallowing disorder that might lead to recurrent
aspiration.
Other, less common causes of cough in infancy include CF, congestive heart
failure, interstitial pneumonitis, and congenital immunodeficiencies.
This patient's history is suggestive of an infectious etiology, because he was in good health
until approximately 1 one week before presentation. However, his history of
prematurity should add one more disease to the differential diagnosis:
bronchopulmonary dysplasia. Such patients are also more likely to develop
reactive airways disease in response to a viral infection.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Diarrhea - Case 17-1: 2-Month-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
In this case, diarrhea was associated with vomiting and a critical physical
finding, that of an inguinal mass. This essential finding directed the
differential diagnosis toward causes of inguinal or scrotal swelling. An
important distinction to make is between a painful and a painless mass. A
hydrocele is a common entity that causes painless inguinal or scrotal swelling.
It is primarily differentiated from an inguinal hernia by the ability to
palpate above the mass, revealing discontinuity between the mass and the
inguinal canal. The mass, as a result, does not change in size with straining
or crying. In addition, a hydrocele is not reducible and usually
transilluminates, although the ability to transilluminate the mass does not
exclude the possibility of an incarcerated hernia.
Another cause of a painful scrotal mass is testicular torsion. There often is no
history of a prior scrotal mass, and in fact there may be a history of
undescended testis. This mass is very tender and does not extend into the
inguinal canal.
Torsion of the appendix testis results in a painful scrotal mass that may appear
as a tender blue nodule on the upper pole of the testis, which itself is not
tender. Inguinal lymphadenopathy may be tender or painless, but the key to
diagnosis is the lateral and inferior location of these nodes in relation to
the inguinal canal. Signs of infection in the area of lymphatic drainage are
also important in making this diagnosis. An inguinal hernia is usually
characterized by a painless swelling in the inguinal area that often increases
in size with crying or straining. Incarceration of the hernia results in
extreme pain and signs of bowel obstruction. If strangulation occurs, bloody
diarrhea may result.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Diarrhea - Case 17-4: 15-Month-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
The chronic nature of his diarrhea for the last 3 months, associated with weight
loss, moved the differential diagnosis away from the diagnosis of acute
infectious diarrhea due to either bacterial or viral causes. A prolonged bout
of postinfectious diarrhea due to disaccharidase deficiency was possible but
unlikely. Chronic diarrhea due to infection with
C. difficile or ova and parasites was a possibility even without a history of antibiotic
use, bloody diarrhea, foreign travel, or use of untreated water sources. The
key observation in making this diagnosis occurred while the patient was in the
hospital: he took nothing by mouth but continued to produce profuse voluminous
watery diarrhea. This finding indicated the presence of secretory, rather than
osmotic, diarrhea. In this differential diagnosis, the list is rather brief and
includes rare congenital and paraneoplastic conditions. Congenital defects in
chloride or sodium transport are more likely to manifest in infancy. Infectious
causes of secretory diarrhea include small-bowel overgrowth or infection with
immuno adherent
E. coli stimulating gastrointestinal secretions. Any cause of villous atrophy, whether
congenital, autoimmune, or secondary to immune deficiency (e.g., HIV infection,
severe combined immunodeficiency) may also result in this presentation.
Neuroblastoma or other tumors of neural crest origin (e.g., ganglioneuroma) may
secrete vasoactive intestinal peptide (VIP), resulting in secretory diarrhea.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Jaundice - Case 15-3: 2-Month-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
The susceptibility of neonates to unconjugated hyperbilirubinemia is favored by
a number of factors, including relative increases in bilirubin production and
enterohepatic circulation along with relative decreases in hepatic uptake and
conjugation. Unconjugated hyperbilirubinemia is a very common occurrence in the
newly born and is usually self-limited and benign. However, if the serum
concentration of bilirubin exceeds 17 mg/dL, the jaundice can no longer be
regarded as physiologic.
Given this predisposition of newborns to an imbalance between bilirubin
generation and hepatic excretory capacity, pathologic or prolonged neonatal
hyperbilirubinemia is often attributable to conditions that exacerbate the
imbalance. For instance, hemolytic diseases (e.g., ABO incompatibility),
polycythemia, and extravascular blood collections (e.g., cephalohematoma,
subgaleal blood, ecchymoses) are conditions that favor increased bilirubin
production. Decreased bilirubin clearance can result from inherited bilirubin
metabolism disorders (e.g., Crigler-Najjar syndrome, Gilbert disease),
hypothyroidism, and circumstances that increase enterohepatic reuptake (e.g.,
breast-feeding, delayed meconium passage). As for older children, Gilbert
syndrome (a genetic disorder of the uridine diphosphoglucuronate
glucuronosyltransferase enzyme system that occurs in about 6% of adults) and
hemolytic anemias are the most common causes of unconjugated bilirubinemia.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Pallor - Case 10-1: 3-Week-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
This male child presented with pallor at a young age. There was no history of
jaundice, which lessened the likelihood of a hemolytic anemia. There was no
issue of dietary causes because of the baby
's young age. No chronic illness was apparent, and there was no history of blood
loss. Therefore, the focus shifted to a congenital defect in RBC production.
There was a remarkable drop in the hemoglobin and a very poor bone marrow
response as far as reticulocyte production. The WBC and platelet concentrations
were normal. The anemia was macrocytic. The sum of these findings indicated a
defect of RBC production. There was also the physical examination finding of a
possible skeletal anomaly at the distal right femur.
RBC aplasia may be congenital or acquired. Most of the acquired forms occur in
adults, but some may be seen in adolescent patients. In childhood, the major
causes are Diamond-Blackfan anemia, transient erythroblastopenia of childhood,
and acquired aplasia of RBCs associated with chronic hemolysis. The aplastic
crisis of a sickle cell disease patient is an example of the latter.
In this case, there was no evidence of acute or chronic hemolysis. The patient
was too young to be considered for transient erythroblastopenia of childhood.
Another possible cause to be considered was Fanconi anemia, an autosomal
recessive disorder associated with aplastic anemia, short stature, skeletal
defects, pigmentation changes, and other abnormalities. Some cases of Fanconi
anemia are diagnosed in the first year of life. The anemia involves all cell
lines; bone marrow analysis and genetic studies establish the diagnosis. In
this case, there was only RBC involvement, and hence Diamond-Blackfan anemia
was the most plausible diagnosis.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Pallor - Case 10-3: 5-Month-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
This child came to the hospital with significant severe pallor of acute onset.
The child had had no medications or unusual exposures. It was clear that he was
critically ill. Despite the severe illness, the WBC and platelet counts were
normal. The most significant finding was the severe anemia. The increased
unconjugated bilirubin and lactate dehydrogenase levels suggested a hemolytic
process. Other causes of hemolytic anemia were considered, including
drug-associated hemolytic anemia, disorders of RBC membrane and cytostructure
(e.g., hereditary spherocytosis), abnormalities of RBC metabolism (e.g., G6PD
deficiency), as well as sepsis with disseminated intravascular coagulation. The
patient was given antibiotics to cover this last possibility. Parvovirus B19
infection can cause severe anemia but usually as a result of bone marrow
suppression rather than hemolysis.
Patients with a microangiopathic hemolytic anemia (e.g., hemolytic-uremic
syndrome, thrombotic thrombocytopenic purpura) usually have schistocytes rather
than spherocytes on peripheral blood smear. Both of these conditions usually
present with severe thrombocytopenia. A child of this age should be closely
examined for physical abnormalities seen with Diamond- Blackfan syndrome or
Fanconi anemia. Laboratory studies allowed differentiation of the diagnostic
possibilities.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Seizures - Case 19-3: 8-Month-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
This infant had seizures related to hypoglycemia. Hypoglycemia in an infant,
defined as a blood glucose concentration of 40 mg/dL or less, warrants
immediate treatment followed by appropriate investigation. Many inborn errors
of metabolism responsible for hypoglycemia manifest during the first year of
life, whereas milder defects of glycogen degradation and gluconeogenesis
manifest in childhood only after prolonged periods of fasting. Causes of
hypoglycemia in an infant include hyperinsulinism, hormone deficiency, and
defects in branched-chain amino acid metabolism, fatty acid oxidation, and
hepatic enzymes.
Urinary ketones are absent or low in children with hyperinsulinism and fatty
acid oxidation defects who present with hypoglycemia. Hypoglycemia secondary to
hyperinsulism most commonly appears during the first year of life. It is
usually associated with islet-cell dysplasia and rarely with islet-cell
adenomas. Insulin is elevated (greater than 5
µU/mL), and injection of glucagon elicits a rapid rise in blood glucose levels.
Children with disorders of fatty acid metabolism can present with hypoglycemia
and profound disturbance of consciousness that may not improve when the plasma
glucose is normalized. In addition to hypoketonemia, they have high plasma free
fatty acid concentrations, elevated ALT and AST, rhabdomyolysis,
cardiomyopathy, and cerebral edema.
The presence of urinary ketones usually suggests hormone deficiency, glycogen
storage disease (GSD), or defects in gluconeogenesis. Hypoglycemia is a common
presentation for infants with panhypopituitarism, isolated growth hormone
deficiency, and absolute (adrenal hypoplasia, Addison
's disease, adrenal leukodystrophy) or relative (congenital adrenal hyperplasia)
glucocorticoid deficiency. Midline defects such as cleft lip or palate, optic
dysplasia, and microphallus suggest anterior pituitary hormone deficiency.
Hyperpigmentation associated with Addison
's disease rarely occurs in young children. Addison's disease is occasionally associated with hypoparathyroidism (hypocalcemia).
Severely compromised adrenal function, as in congenital adrenal hyperplasia,
may lead to serum electrolyte disturbances or ambiguous genitalia.
Children with branched-chain ketonuria (maple syrup urine disease) excrete
urinary ketoacids that impart the characteristic odor of maple syrup.
Clinically, these infants have frequent hypoglycemic episodes, lethargy,
vomiting, and muscular hypertonia. GSDs are inherited autosomal recessive
defects that are characterized by either deficient or abnormally functioning
enzymes involved in the formation or degradation of glycogen. Hepatomegaly,
growth failure, hyperlipidemia, and hyperuricemia are common clinical features.
Other disorders to consider include galactosemia, especially in children with
hepatosplenomegaly, jaundice, and mental retardation; and
fructose-1,6-diphosphatase deficiency, in children with hepatomegaly due to
lipid storage but only mildly abnormal liver function studies.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Vomiting - Case 3-1: 7-Week-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
Vomiting in early infancy can be a very worrisome symptom. The most common cause
of emesis in this age group is GER, either physiologic or due to overfeeding.
Anatomic obstruction should always be considered. Obstructive lesions include
malrotation with a volvulus, intestinal or esophageal atresia, pyloric
stenosis, congenital adhesions or bands, incarcerated hernia, intussusception,
and Hirschsprung
's disease. The level of the obstruction determines whether the vomitus is
bilious and whether the abdomen is distended. Infectious causes include
gastroenteritis, urinary tract infection, meningitis, pneumonia, and
pericarditis. Bloody streaks in the emesis could be the result of a milk
protein allergy, gastroenteritis, necrotizing enterocolitis, or achalasia.
Metabolic disorders must be considered in this child who presents with vomiting
and a significant metabolic acidosis. Etiologies such as congenital adrenal
hyperplasia (CAH), adrenal hypoplasia, inborn errors of metabolism including
both amino acid and organic acid disorders, and galactosemia must also be
considered.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Wheezing - Case 1-3: 5-Week-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
In this 5-week-old boy with respiratory distress and lobar consolidation, the
most likely diagnosis is bacterial pneumonia with pleural empyema. Etiologic
organisms in this age group include group B
Streptococcus, Listeria monocytogenes, and gram-negative enteric bacilli. The radiographic appearance of the lung may
suggest a congenital lung malformation such as pulmonary sequestration,
bronchogenic cyst, or cystic adenomatoid malformation. Infantile lobar
emphysema is unlikely because the lung, despite causing a mediastinal shift,
does not appear to be overinflated. Other congenital considerations include
enterogenic cysts and CDH. Acquired causes include mediastinal neoplasm (e.g.,
neuroblastoma) and chronic pulmonary infection distal to an aspirated foreign
body or an area of bronchiectasis. Chronic pulmonary infection may result in
neovascularization of the infected tissue by ingrowth of systemic arteries.
Such acquired systemic vascularization typically consists of several small
arteries rather than one or two large arteries that typically supply a
pulmonary sequestration. It may be impossible to make the distinction between
true pulmonary sequestration and so-called pseudosequestration secondary to
chronic infection preoperatively.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Wheezing - Case 1-5: 5-Week-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
In an infant with cyanosis and respiratory distress, bacterial or viral sepsis
must be considered. Children with either viral bronchiolitis or pertussis may
present with cyanosis, respiratory symptoms, and rapid deterioration. In this
child, the history of periodic cyanosis with crying since birth provided a clue
to the diagnosis. The differential diagnosis includes a large ventricular
septal defect, patent ductus arteriosus, truncus arteriosus, atrioventricular
canal, single ventricle without pulmonary stenosis, and total anomalous
pulmonary venous connection (TAPVC). Except for TAPVC, these cardiac anomalies
typically produce electrocardiographic evidence of left atrial or left
ventricular hypertrophy. Children with TAPVC have right ventricular
hypertrophy. The severity of illness warranted an echocardiogram, which
provided the definitive diagnosis.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
Wheezing - Case 1-6: 4-Month-Old Boy:
I. Differential Diagnosis
(Pediatric Complaints and Diagnostic Dilemmas)
The most common cause of progressive respiratory distress during infancy is
bronchiolitis, which is most often caused by respiratory syncytial virus;
adenovirus; influenza viruses A and B; or parainfluenza viruses types 1, 2, and
3. The differential diagnosis of perihilar or diffuse infiltrates includes
B. pertussis, C. trachomatis, and M. pneumoniae. Herpes simplex virus and cytomegalovirus (CMV) can cause pneumonia in the
young infant. CMV pneumonia is frequently associated with hepatosplenomegaly,
thrombocytopenia, and lymphocytosis. PCP should be considered, particularly if
there are maternal risk factors for HIV infection. Other conditions
predisposing to PCP include primary B-cell defects, primary T-cell defects, and
combined defects. The immune disorders most likely to result in PCP are severe
combined immunodeficiency, DiGeorge anomaly, Wiskott-Aldrich syndrome, X-linked
agammaglobulinemia, and hyper-IgM syndrome.
Noninfectious causes of pneumonia include GER associated with pulmonary
aspiration. Occasionally, an anatomic defect such as TEF may predispose to
aspiration. Primary cardiac abnormalities (e.g., ventricular septal defect),
pulmonary vascular abnormalities, and impaired lymphatic flow (e.g., congenital
lymphangiectasia) can cause tachypnea and progressive respiratory distress in a
4-month-old child. Cystic fibrosis can masquerade as any of these conditions.
» READ BOOK EXCERPT ONLINE »
Source: Pediatric Complaints and Diagnostic Dilemmas, 2003
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