Correct!
3. Serum alpha1-protease inhibitor level
An anterior abdominal wall fat pad biopsy may be used to assess for the presence of amyloidosis, but that diagnosis is not a consideration for this patient’s presentation and imaging. Biopsy of fat could potentially detect panniculitis as well, which could be suggestive of a particular diagnosis for this patient, but this would merely constitute indirect information, and there is a choice provided above that is capable for directly suggesting a diagnosis for this patient. 99mTc-MAA ventilation – perfusion scanning is typically used to asses for suspected pulmonary embolism and is occasionally used to determine relative perfusion to each lung, often as part of a pre-operative assessment prior to thoracic surgery. The ventilation portion of this study would be capable of showing air trapping, but given the thoracic CT appearance, airflow obstruction is certainly present, so 99mTc-MAA ventilation – perfusion scanning is unlikely to add new, useful information. Thoracic MRI performed with intravenous contrast would provide little information to that already known with thoracic CT, and, in fact, would be largely incapable of yielding useful information regarding the lung parenchyma. A serum angiotensin converting enzyme level can be used to suggest the presence of lung disease, as in the case of sarcoidosis, but normal levels would be non-contributory, whereas elevated levels would provide little useful direction towards establishing a diagnosis.
The patient’s serum level of alpha1-protease inhibitor level was found to be diminished- 7 µmol (normal values range from 20 - 48 µmol; emphysema rarely seen with levels greater than 11 µmol). Based on this finding, he underwent further phenotypic testing, which disclosed the Pi ZZ (homozygotic) phenotype of plpha1-protease Inhibitor deficiency.
Diagnosis: Panlobular emphysema due to alpha1-protease inhibitor deficiency
References