Nontuberculous mycobacterial infection: CT scan findings, genotype, and treatment responsiveness.
OBJECTIVE
The purpose of this study was to compare the imaging findings of nontuberculous mycobacterial (NTM) infection in patients with normal and abnormal cystic fibrosis (CF) genotypes, and normal and abnormal alpha1-antitrypsin (AAT) phenotypes.


METHODS
A retrospective review of medical records and chest CT scans from 85 patients with microbiologically proven NTM infection was performed. All patients had undergone genotype analysis for CF mutations, and phenotypic evaluation for AAT status. Patients with homozygous CF or AAT were not included. Two independent observers assessed the patterns and distribution of disease, according to a standardized score sheet. In 52 patients, follow-up CT scans were obtained 1 to 46 months (mean duration, 8 months) following the initial CT scan. The CT scan findings on the follow-up scan were visually compared with those on the initial CT scan for progression or regression of abnormalities. Statistical analysis was performed to evaluate the relationship between the dominant CT scan pattern and CF/AAT status, and between CT scan pattern and radiologic change on follow-up.


RESULTS
Fifteen patients (18%) were found to carry a single CF mutation, and an abnormal AAT phenotype was seen in 13 patients (15%). Three patients (3%) were found to have both a heterozygous CF mutation and a heterozygous AAT phenotype. On the initial CT scans, bronchiectasis and nodules were the most frequent findings of NTM infection in all three groups (p > 0.05). The prevalence of nodules was slightly lower in the CF group, and the prevalence of linear scarring was greater in the AAT group than in the normal group (p < 0.05). Among the 52 patients who had a follow-up CT scan, 8 (15%) had a CF mutation and 6 (12%) had an abnormal AAT phenotype. The extent and pattern of abnormality seen on the initial CT scan did not predict change on follow-up evaluation. After treatment, 40 patients (56%) with a normal CF genotype had decrease in disease extent, compared with 4 patients (25%) with a CF mutation (p < 0.05). Bronchiectasis was improved in approximately 35% of those with normal genotype, but in none of those with a CF mutation.


CONCLUSIONS
In patients with NTM infection, the CT scan findings show only minor differences according to phenotype and genotype. Initial CT scan findings do not predict change on follow-up CT scan evaluation. However, on follow-up CT scan, patients with CF mutations are less likely to improve, while those with AAT phenotype appear to have a radiographic outcome similar to those with normal phenotype.
Kim
Jeung Sook
JS
Department of Radiology, University of Colorado H. S. C., 4200 East Ninth Ave, Box A030, Denver, CO 80220, USA.
Tanaka
Nobuyuki
N
Newell
John D
JD
Degroote
Mary A
MA
Fulton
Kayte
K
Huitt
Gwen
G
Lynch
David A
DA
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003550:Cystic Fibrosis / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000235:genetics / Q000628:therapy*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005838:Genotype; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009164:Mycobacterium Infections / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000235:genetics / Q000628:therapy*; D011237:Predictive Value of Tests; D012016:Reference Values; D012189:Retrospective Studies; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D019896:alpha 1-Antitrypsin Deficiency / Q000235:genetics