Could my son have Cystic Fibrosis?
My son who is 8 had started with what Dr's told was Asthma at 6 months old. As the years go on they still say it is Astma, But the symptoms and attacks get worse. He started at a year old with just 1 medication. Now he is on 6 Daily meds. We have Done CF test that come back Neg. Yet I was told when they do testing they only test for 13 (major) kinds of CF when there are about 1,000 mutations of CF. We have been to PCP's allergy specialist, Asthma Specialist, Pulmonologist, They all say Asthma (I swear they all agree cause they are all in the same practice). On top of all this he has the clubbed fingers a signs of CF. Anyone have any ideas on where or who to see next?
Answer by John D
My next course of action would be to see a CF specialist; it may sound stupid, but start by googling "cystic fibrosis specialists," and see if there's one whose practice is in your area. I know a predisposition to CF is genetically linked, so perhaps you should see a medical geneticist and have yours, your spouse's, and then your son's DNA examined for the CF gene--CF manifests if and only if both parents carry the gene and the child inherits one copy from each parent, so, even if both you and your spouse are carriers, there is, at best, a 25% chance your son will have inherited the disease. Clubbing could also be indicative of many other issues--or nothing at all--so be sure to have your son checked for other diseases typically associated with clubbing. Good luck.
Answer by Susan S
Your son may not have CF.
There are many causes of finger clubbing, too numerous to mention here. Note that CF has numerous Gastrointestinal signs as well. Also, has your son had all the tests below?
Lab Studies
The diagnosis of cystic fibrosis (CF) is based on typical pulmonary and/or gastrointestinal tract manifestations, a family history, and positive results on sweat test.
Sweat test: Several methods are used to conduct a sweat test. Performed properly, the quantitative pilocarpine iontophoresis test (QPIT) to collect sweat and perform a chemical analysis of its chloride content is currently considered to be the only adequately sensitive and specific type of sweat test (see Cystic Fibrosis Foundation).
For reliable results, collect at least 50 mg or, preferably, 100 mg of sweat. Current macroduct collection methods allow adequate analysis with smaller volumes of sweat. The sweat chloride reference value is less than 40 mEq/L, and a value of more than 60 mEq/L of chloride in the sweat is consistent with a diagnosis of CF. The sweat test must be performed at least twice in each patient, preferably several weeks apart. Values of 40-60 mEq/L are considered borderline, and the test must be repeated because these values have been found to be consistent with the diagnosis in some patients with typical features.
Repeat a sweat test to confirm positive results. Repeat a sweat test with negative results if clinical features suggestive of CF are present. Some patients with genetically documented CF and typical symptoms have consistently negative results on sweat tests.
Other causes of elevated levels of sweat chloride include the following:
Untreated adrenal insufficiency
Glycogen storage disease
Type I fucosidosis
Hypothyroidism
Vasopressin-resistant diabetes insipidus
Ectodermal dysplasia
Malnutrition
Mucopolysaccharidosis
Panhypopituitarism
Familial cholestasis
Familial hypoparathyroidism
Atopic dermatitis
Iatrogenic causes (ie, infusion of prostaglandin E1, improper technique)
Imaging Studies
Chest radiography: Initial changes are hyperinflation and peribronchial thickening. Progressive airtrapping with bronchiectasis may be apparent in the upper lobes. With advancing pulmonary disease (see Image 1), pulmonary nodules resulting from abscesses, infiltrates with or without lobar atelectasis, marked hyperinflation with flattened domes of the diaphragm, thoracic kyphosis, and bowing of the sternum develop. Pulmonary artery dilatation and right ventricular hypertrophy associated with cor pulmonale is usually masked by marked hyperinflation. Several radiologic scoring systems exist.
Sinus radiography: Panopacification of the sinuses is present in almost all patients with CF, and its presence is strongly suggestive of the diagnosis. Conversely, absence of panopacification strongly suggests that CF is not present.
Other Tests
Genotyping
More than 1300 CF mutations have been identified. In the commercially available CF gene sequencing method, the entire coding region, splice junction sites, and promoter region of the CFTR gene are amplified from genomic DNA by polymerase chain reaction (PCR) and the subjected to nucleotide sequence analysis on an automated capillary DNA sequencer. This test can detect more than 98% of disease-causing mutations. The detection rate is lower in African American, Hispanic, and Asian populations; therefore, failure to find 2 abnormal genes does not exclude the disease.
A finding of 2 CFTR mutations in association with clinical symptoms is diagnostic, but negative results on genotype analysis do not exclude the diagnosis.
Semen analysis: Obstructive azoospermia, in the absence of any other obvious cause (eg, vasectomy), provides additional corroborative evidence for the diagnosis of CF. Confirm results from semen analysis by obtaining a testicular biopsy.
Nasal potential difference measurement
Potential difference (PD) (voltage) measured from nasal mucosa and the reading obtained by a reference electrode inserted into the forearm correlates with the movement of sodium across cell membranes, which is a physiologic function rendered abnormal by a CFTR mutation. The nasal potential difference (NPD) is a sensitive test of electrolyte transport that can be used to support or refute a diagnosis of CF. A normal mean value standard error (SE) is 0.9-24.7 mV; an abnormal value is 1.8-53 mV. When measurements are repeated after mucosal perfusion with amiloride to block an epithelial sodium channel, the drop in PD is greater in patients with CF (73%) than in control subjects (53%). Normally, subsequent perfusion with chloride-free solution and isoproterenol produces a sharp increase in the PD but has little effect when CFTR function is abnormal.
As a result of the lack of commercially available equipment and the practical difficulties with NPD measurement, this test is performed in only a few research centers to diagnose CF in patients in whom making a diagnosis is difficult or a sweat test is not technically possible because of skin problems.
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