MRI and Biomarkers in Early Detection of Pulmonary Changes in Ataxia-Telangiectasia

Introduction

Ataxia-Telangiectasia (A-T; OMIM#208900) is rare an autosomal recessive disorder with early childhood onset and characterized by progressive ataxia, telangiectasia, sinopulmonary infections, hypersensitivity to ionizing radiation, immunodeficiency, and increased cancer risk [1]. The general world prevalence of A-T is estimated at 1 in 40 000 to 100 000 live births. A-T affects both sexes [2]. A-T is caused by mutations in an ataxia-telangiectasia-mutated (ATM) gene located on chromosome 11q22-23 and encoding a serine/threonine protein kinase, which results in either the absence of ATM protein or ATM kinase activity [3]. The ATM protein is responsible for formation of TCR receptors on T lymphocytes and immunoglobulins (Ig) by participating in V(D)J gene recombination and CSR recombination in mature B lymphocytes. Thus, dysfunction or lack of ATM protein is the cause of immunodeficiency and, consequently, pulmonary complications can occur. Mutations are associated with increased chromosome breakage, cellular aging, impaired double-stranded DNA repair, and inflammation [4,5]. Immunodeficiencies affect about 70% of patients with A-T. Cellular immune deficiencies are present in almost all patients with A-T, often in the form of B or T lymphocyte lymphopenia and reduced CD8+ and/or CD4+ T cells [6]. Humoral immune deficiency is more variable, with impaired production of specific antibodies, selective IgA deficiency, hypogammaglobulinemia, and deficiency of IgG subclasses [7].

Moreover, swallowing dysfunction during meals and cough discoordination during infections in these patients can increase the risk of pneumonia [8]. Respiratory diseases in A-T patients progress with age and deterioration of the neurological condition. Lung disease occurs in over 70% of A-T patients and more than 25% of them develop chronic lung disease [9,10]. Patients with A-T have a poor prognosis, with a survival time of about 25 years. The 2 most common causes of death in these patients are chronic lung disease and malignancies [10,11]. Lung disease is a significant cause of morbidity and mortality in people with A-T. Individuals with A-T are at higher risk for recurrent lung infections, developing bronchiectasis and interstitial lung disease (ILD), in part due to their immunodeficiency [5,12–14].

Other, non-infectious lung lesions in A-T may be associated with the presence of lesions secondary to lung lymphoma, which can clinically and radiologically mimic ILD [15,16]. In addition, chemotherapy used to treat cancer in A-T patients may also be associated with an increased risk of pulmonary fibrosis [17]. The risk of acute respiratory failure with chemotherapeutic agents such as bleomycin is well described and may be due to an underlying DNA repair defect [16]. These agents are used with great caution in A-T patients because they can have the same effect on cells as ionizing radiation [17]. Sensitivity to ionizing radiation and shortened telomeres, characteristic for A-T, can increase the risk of complications, such as pulmonary fibrosis, when malignancies are treated [17–19].

Exposure to X-rays should be limited to necessary diagnosis only. Radiation therapy for cancer or any other reason is not recommended for patients with A-T and should only be used in reduced doses in rare cases [20].

Early detection of the presence or progression of structural lung disease is essential to develop preventive or therapeutic strategies. Imaging techniques, in particular computed tomography (CT), are considered the criterion standard for structural lung disease diagnosis. Patients with A-T have higher radiation sensitivity. Thus, because the exact level of “safe” radiation exposure is unknown, clinicians should consider a risk-benefit assessment when ordering CT scans. Magnetic resonance imaging (MRI), being radiation free, is emerging as a new diagnostic modality in thoracic imaging, particularly in patients with radiosensitivity [21].

Lung MRI has been shown to be a reliable imaging modality in patients with COPD, cystic fibrosis, and other lung diseases [22–24]. The main advantage of MRI is the ability to obtain high-resolution cross-sectional images without the use of ionizing radiation and it is an alternative to CT. MRI of the lungs has been used in many patients with congenital immune disorders and hypersensitivity to ionizing radiation, such as A-T or CVID [4,23].

Serum amyloid A- and C-reactive proteins are high-sensitivity and -specificity biomarkers and are valuable diagnostic tools for early diagnosis of inflammation [25]. An acute-phase protein, CRP, synthesized by liver, is a more widely used clinical indicator of inflammation than SAA, and changes in its concentration can reflect the degree of inflammatory response, mainly due to bacterial infection [25]. Serum amyloid A (SAA) is an acute-phase protein mainly synthesized by the liver. In the case of inflammatory response, the SAA level significantly increases rapidly to a maximum within 8–12 hours by up to 1000-fold during inflammation, and rapidly return to normal levels after the inflammation has subsided. High concentrations of SAA are found in various neoplastic processes, including cancer of the stomach, lungs, kidneys, colon, prostate, nasopharynx, and breasts [26]. They are correlated with the aggressive course of the tumor and indicate an unfavorable prognosis. The sensitivity of SAA for the diagnosis of some diseases is significantly better than that of CRP [27], and the SAA concentration often increases before symptoms of infection appear in the early stage of viral and bacterial infections [28]. Moreover, SAA, as a newer parameter than CRP, is currently attracting more attention. Both SAA and CRP are correlated with clinical indices of patients with acutely exacerbated chronic obstructive pulmonary disease [29]. Moreover, SAA has been associated with a significant increase in serum levels in various chronic inflammatory diseases, with a rapid decline to normal level after recovery. Serum SAA and CRP of children with pneumonia are highly expressed, so they can be used as markers for early diagnosis of pneumonia [30].

The aim of this study was to assess whether lung MRI accompanied by measurement of the acute-phase proteins CRP and SAA could be a useful diagnostic tool for early detection of pulmonary alterations in A-T patients.

Material and Methods

MAGNETIC RESONANCE IMAGING (MRI) PROTOCOL:

All patients were examined using 1.5 T MR scanners (Sola or Avanto fit, Siemens, Germany). These patients underwent imaging of the thorax from lung apices to the domes of the diaphragm.

The imaging protocol consists of: t2_tse_blade_fs in coronal, axial, and sagittal planes; trufi single shot in coronal, axial, and sagittal planes; ep2d_diff_b50_400_800 with ADC map; and optionally t1_starvibe_tra_fs. No gadolinium-based contrast agents were administered. The MRI examination was completed within 30–40 minutes.

Based on MRI findings, patients were qualified into 4 categories (from 0 to 3). Category 0 patients had a normal lung picture, category 1 patients had a single enlarged lymph node in the hilum of the lungs, category 2 patients had single streaked changes, and category 3 patients had severe bronchial and parenchymal alterations.

SAA AND CRP MEASUREMENT:

Peripheral blood (9 ml was collected on a “clot” tube) in a vacuum system without anticoagulant as part of routine diagnostics. Samples had to be completely clotted. The samples were centrifuged (RT, 10 min, 3000 rpm) to obtain serum. After centrifugation, they could not contain any particles. Lipemic or turbid samples were clarified by re-centrifugation of the serum (10 min, approximately 15 000×g) before testing. The measurement of CRP and SAA were performed immediately.

The serum amyloid A (SAA) was measured by nephelometry method on an automated Atellica^® NEPH 630 (Siemens Healthcare, Germany) device using high-specificity monoclonal antibodies (measurement of light scattered in the sample) with initial measurement range 3–200 mg/L, reference range <6.4 mg/L, and total precision CV ≤6.4%.

The C-reactive protein (CRP) was measured on an Abbott Alinity C Chemistry Analyzer (Abbott Diagnostics, Germany) device using quantitative immunoturbidimetric determination in human serum with wide range (0.10–48.0 mg/dl), reference range <0.5 mg/dl, total precision CV 3.1%.

No statistical analysis was performed due to the small sample size. Own interpretation of the results based on observations of the obtained data.

Results

CLINICAL EVALUATION:

The study included 27 patients with diagnosed A-T syndrome. The mean age at the time of diagnosis was 5.9 years (range, 2–26 years.). All patients presented symptoms of progressive cerebellar ataxia from the first years of life; 15 of them (55%) were wheelchair-dependent (Table 1).

All patients underwent diagnostic testing, including assessment of serum IgA and alpha-fetoprotein concentration. Ataxia-telangiectasia (A-T; OMIM#208900) was diagnosed based on the European Society of Immunodeficiency criteria. The diagnosis of this rare disease was confirmed by genetic tests.

Depending on the frequency and severity of respiratory infections occurring during the last 3 years of observation (2018–2021), patients were divided into 4 groups (Tables 2). Group 1 consisted of 14 patients without or sporadic infections (1–2 infections per year, mainly of the upper respiratory tract); group 2 consisted of 8 patients with only common upper respiratory tract infections (more than 2 infections per year); group 3 contained 4 patients with more than 1 respiratory infection per year, such as sinusitis, bronchitis, mild pneumonia but not requiring hospitalization; and group 4 had 1 patient with frequent and more serious infections such as at least 1 serious case of pneumonia requiring hospitalization, chronic bronchitis, and bronchiectasis.

In the study group, 6 patients (females) received immunoglobulins due to IgG and/or IgG subclasses deficiency. Three of them had sporadic respiratory tract infections (group 1), and the remaining 3 were qualified to groups 2, 3 and 4, respectively. In this group, analysis by MRI showed the presence of severe bronchial and parenchymal alterations in 2 patients, 2 had only 1 enlarged lymph node, and the in the remaining 2 patients no changes were found.

In addition, in 4 of the 27 patients with decreased concentration of IgG and/or IgG subclasses, substitution with immunoglobulins has not been required yet.

MRI CATEGORIES IN A-T PATIENTS AND INFLAMMATION BIOMARKERS:

MRI made it possible to distinguish the following groups of patients depending on the severity of the respiratory tract infection and/or changes in the lungs (Tables 3).

Characteristics of patients according MRI category are presented in Figure 1. Of the 14 patients without lung lesions on MRI (category 0), 9 were in group 1, 4 were in group 2, and 1 to the infection group 3. In patients with only 1 enlarged lymph node in the cavities (MRI category 1), 1 was in group 1, and 2 were in group 2. Among the 6 patients with MRI category 2, 4 were in group 1, 1 was in group 2, and 3 were in group 3. Among the 4 patients with the most severe lung lesions, 1 was in group 2, 2 were in group 3, and 1 was in group 4.

In the entire study group, 14 patients had no respiratory tract infection, 8 had occasional respiratory infections, 4 had single bronchitis or pneumonia, and 1 patient had chronic bronchitis. In 4 patients who did not have frequent infections of the respiratory system, classified to group 1, there were changes in MRI of the lungs (category 2). In this group, only 1 patient had a high concentration of SAA.

Six patients (all females) in the study group received immunoglobulins due to IgG and/or IgG subclasses deficiency. Two of them had severe of bronchial and parenchymal alterations, but 2 patients had no changes, and the remaining 2 patients had only single enlarged lymph nodes. Three of them had sporadic respiratory tract infections, and 1 each were assigned to group 1, 3, and 4. Four patients had low concentrations of IgG and/or IgG subclasses, which did not yet require substitution with immunoglobulins. Three of these 6 patients had no MRI changes of the lungs, 1 had single streaked changes, 2 had no infections, 1 had sporadic upper respiratory tract infections, and 1 was assigned to group 3.

Two patients (siblings) died due to respiratory complications, at ages 31 and 28. One of the deceased was classified to group 3 and the other was assigned to group 2. Both had extensive pulmonary lesions on MRI, which were correlated with an increase in markers of SAA inflammation.

In the 11 patients who underwent lung MRI twice compared to the first MRI, 2 patients had new lesions and 1 patient had regression of inflammatory lesions. In the remaining patients, no new lesions appeared. The patient with regression of lung lesions from category 3 to 2 received antibiotic prophylaxis after the first lung MRI. Two females with progression of lung disease from category 2 to 3 also had significant increases in SAA level.

Figure 1 shows the relationship between the infectious groups and category of observed changes in MRI of the lungs (Figures 2, 3).

SEROLOGICAL INFLAMMATION MARKERS:

Simultaneously with the MRI, in all 27 determinations of SAA in serum samples was performed and its elevated values were observed in 11 of them (41%). In 9 subjects, the SAA concentrations ranged from 7.06 to 19.2 mg/L, and 2 patients had values of 190 and 201 mg/L (there were the 2 oldest patients, aged 30.1 and 28.5 years). Among the 11 patients with elevated SAA, 4 had no changes in the lung MRI (category 0), 3 were in group 1, and 1 was in group 3. In the remaining 7 patients, 4 had changes in the lung MRI classified into category 3, and 3 had changes classified to category 2. In 2 patients, worsening lung changes observed in the second MRI analysis were accompanied by significant increase in serum SAA (162 mg/L and 175 mg/L). Elevated concentrations of SAA were more frequently observed in patients with pulmonary lesions found by MRI. CRP testing was performed on all patients, and only 4 patients had high values. All these patients had extensive changes in the lungs (MRI category 3) and belonged to the infection groups 3 or 4. Four patients with simultaneously elevated CRP and SAA concentrations had lesions, belonging to category 3 (according to the MRI), and had infections characterizing group 3 (mostly) and group 4 with very high SAA (201 mg/l) (Table 4).

Discussion

MRI STUDY:

Ataxia-telangiectasia (A-T) is a rare and progressive disease that has many complex and diverse manifestations which vary with age. In our study, we presented the importance of MRI in the diagnosis of pulmonary lesions in patients with A-T after infections and the determination of inflammatory parameters such as CRP and SAA at the same time.

Patients with A-T die prematurely because of respiratory diseases (interstitial lung disease/pulmonary fibrosis) and cancer [31]. Frequent pulmonary infections are the main comorbidities in A-T leading over time to chronic lung disease. These patients are at a higher risk of acquiring lung infections. Regular screening for pulmonary complications is important and strongly recommended for all patients with inborn errors of immunity (IEI) [32,33]. Therefore, early and correct pulmonary diagnostics of these patients is very important in monitoring their health and is usually associated with an improved prognosis and applying prompt treatment. Imaging techniques, clinical tests, and laboratory studies play an important role in detecting, characterizing, and quantifying the extent and type of lung damage.

Chest high-resolution computed tomography (HRCT) is the standard method used in the assessment of structural lung damage due to its excellent spatial resolution, speed, and wide availability [33]. Lung ultrasound is a complementary examination. HRCT is the first-line imaging method for early diagnosis of lung diseases and for treatment response evaluation.

However, should be considered that it leads to significant radiation exposure to the patient. On the other hand, increased radiosensitivity has been described in patients affected by many IEI, such as A-T, caused by defects in DNA repair pathways. Many researches in vitro on fibroblasts and lymphoblasts from A-T homozygotes showed increased sensitivity to ionizing radiation and several radiomimetic and free-radical producing agents [4,31]. These patients have an increased risk of lymphoproliferative diseases and cancer [34]. Therefore, patients with A-T should be protected from diagnostic and therapeutic procedures using ionizing radiation, and radiation therapy for cancer should be avoided in these patients, and use of ionizing radiation tests such as HRCT should be minimized. Chest MRI was proposed as a potential alternative for the lungs in the late 1980s [35]. This technique is safe and plays a crucial role in the diagnostic process and monitoring of children with A-T. It is needed in detecting and tracking disease complications associated with infections, inflammation, lymphoproliferation, organ-specific immunopathology, and malignancy. The present study confirms the importance of cooperation between radiologists and immunologists in the assessment of lung parenchyma changes, inflammation of the respiratory tract, and other diseases in A-T, which was also emphasized by studies from other scientific centers [36]. MRI is totally radiation free and provides the best tissue characterization.

The current study shows the efficacy of chest high-field MRI in assessment of severity and extension of pulmonary changes in children and young adults with A-T. Some previous studies have also focused on A-T patients who underwent lung MRI. In 2013, Italian scientists published the first study assessing the severity and extent of changes in the lungs using MRI and its correlation with clinical, microbiological, and functional data in 15 patients with AT with a mean age of 11.3 years (range, 6–31). Although the study group was smaller than our group, it confirmed that chest MRI is a valuable, safe, and radiation-free imaging technique for identifying pulmonary abnormalities in all patients, both symptomatic and asymptomatic [37]. Spirometry provides the best assessment of lung function, but it is difficult to perform reliably because of progressive neurodegeneration in some patients.

MRI AND INFLAMMATION BIOMARKERS:

There are only isolated reports in the world literature on performing lung MRI in patients with primary immunodeficiencies and increased radiosensitivity [23,37–40]. In our study, 38 MRIs of the lungs were performed, including 11 patients in whom examination was completed twice. Among patients in whom lung MRI was performed twice, regression of inflammatory lesions was observed in 1 case. This patient, with regression from group 3 to 2, received antibiotic prophylaxis after the first lung MRI. In contrast, 2 females with progression of lung disease from category 2 to 3 had significant increases in SAA concentration.

Although 14 of 27 (51%) of our patients had no history of recurrent respiratory tract infection, only in 4 (15%) had severe bronchial and parenchymal alterations. Nevertheless, chronic lung disease develops in more than 25% of patients with AT [40–42].

Ataxia-telangiectasia is a rare disease, so statistical analysis could not be performed in this small study group. We emphasize the importance of performing imaging studies, MRI of the lungs, and simultaneous monitoring of inflammatory markers such as CRP and SAA.

we found that SAA concentration was associated with the severity of infection and changes in the lung found by imaging. High SAA levels were associated with frequent sinusitis, bronchitis, and mild pneumonia (group 3: SAA 13–175 mg/L), pneumonia requiring hospitalization (group 4: SAA 201 mg/L), and severe lung MRI changes. SAA can be used as an effective index for A-T diagnosis and treatment. It also may be a good marker for monitoring for exacerbation of infectious respiratory diseases.

The present study suggests that SAA can provide useful prognostic information for the early detection of infection. However, our study has certain limitations. First, standard spirometry was not performed and we could not compare it with parameters such as prognostic factors, FEV1, and PaO2. Moreover, it was conducted on a relatively small number of intragroup participants due to the rarity of A-T, which is a major limitation of this study, and we were unable to perform statistical analyses. However, based on our observations of the relationship between concentration of SAA and the lung image, as well as existing publications regarding lung diseases such as COPD-related inflammation, we conclude that SAA may be useful in the assessment in monitoring the severity of respiratory infections [43]. We also could not perform microbiological tests to confirm the type of infection. There is a need for larger studies assessing the type of infection and the determination of other additional inflammatory parameters to determine the best predictor of pulmonary lesions. It is important that children with A-T should undergo annual lung function studies starting at 6 years of age. Early screening for decline in lung function can allow for earlier interventions (eg, chest physiotherapy, antibiotic therapy, gamma globulin supplementation) [41,42,44]. Longitudinal evaluation studies on larger cohorts of patients with primary immunodeficiency and radiosensitivity and monitoring of treatment response in this disease are needed. Further studies on larger cohorts of patients with A-T are required to expand knowledge regarding specific indications of MRI in A-T, and we believe that this non-ionizing radiation technique will prove to be a useful laboratory tool for monitoring lung disease over time.

Conclusions

DECLARATION OF FIGURES’ AUTHENTICITY:

All figures submitted have been created by the authors who confirm that the images are original with no duplication and have not been previously published in whole or in part.