HIGH RISK INFANT: Cystic Fibrosis (CF)

I. Definition

- is a genetic disease that affects many organs and lethally impairs pulmonary function
- When first described, CF was called “fibrocystic disease of the pancreas” but additional research reveals that this disorder represents a major dysfunction of all exocrine glands
- is hereditary and transmitted as an autosomal recessive trait


II. Etiology

- abnormality of the long arm of chromosome 7
- caused by a mutation in a gene called the cystic fibrosis transmembrane conductance regulator(CFTR)


III. Incidence/ Prevalence

- US: 1 in 3,300 white children and 1 in 16, 300 black children
- Males and females are affected equally

IV. Pathophysiology

The normal gene produces a protein, CFTR, which serves as a channel through which chloride enters and leaves cells. The mutated gene blocks chloride movement, which brings upon the apparent signs of CF.

The blocking of chloride transport results in a change in sodium transport; thus in turn results in abnormal secretions of the exocrine (mucous producing) glands that produce thick, tenacious, rather than thin, free-flowing secretion normally produced.

This abnormal mucus leads to obstruction of the secretory ducts of the pancreas, liver, and reproductive glands. Thick mucus obstructs the respiratory passages, causing trapped air and over inflation of the lungs. In addition, the sweat and salivary glands excrete excessive electrolytes, specifically sodium and chloride.



V. Types

Type Error
I Zero CFTR is produced

II CFTR is not processed correctly, so no protein gets to the cell membrane

III The CFTR chloride pathway is regulated differently than normal, but transfer of CFTR occurs

IV The chloride current is not conducted properly, so transfer of CFTR is slowed

V Synthesis of CFTR is abnormal; however, CFTR is transferred


VI. Clinical Manifestations

Pancreas Involvement

• Steatorrhea
• Protuberant abdomen
• malnutrition – emanciated extremities and loose, flabby folds of skin on their buttocks
• Fat-soluble vitamin deficiencies
= CELIAC SYNDROME

Others:

 Meconium ileus
 Rectal prolapse



Lung Involvement

• Pooled secretions of the bronchioles
• Secondary emphysema
• Bronchiectasis
• Pneumonia
• Atelectasis
• Anterior-posterior diameter of the chest becomes enlarged
• Respiratory acidosis


Sweat Gland Involvement
- Newborn tastes salty when kissed



VII. Diagnostic exam

• Sweat Chloride Analysis

The defect in chloride movement prevents absorption of sodium chloride in the sweat glands; thus more chloride than normal is present in the sweat.

The sweat chloride test is positive for CF when the chloride level in the sweat ranges between 60 and 200 mEq/L (mmol/L), compared with the normal value of 20 mEq/L.

• Duodenal analysis
• Serum immunoreactive trypsin
• Pulmonary testing
• Stool analysis






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Sources:

Adele Pillitteri, 5th Ed. Maternal & Child Health Nursing: Care of the Childbearing & Childrearing Family. Volume 2 pages 1269-1274

Klossner, Hatfield, Introductory Maternity & Pediatric Nursing p.829 – 837

Ignatavicus, Workman. Medical – Surgical Nursing Critical Thinking for Collaborative Care. p. 607 - 609

http://en.wikipedia.org/wiki/Cystic_fibrosis#Pathophysiology

http://ccn.aacnjournals.org/cgi/reprint/25/4/46.pdf