Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Birt-Hogg-Dube syndrome
- Radiologic Findings
- Fig 1-4. Axial and coronal reconstructed chest CT scans show multiple air cysts of varying size abutting vascular bundles in both lungs with lower predominancy. The cysts showed lobulated or multi-septated appearance.
Fig 5. KUB CT scan shows an avidly arterial enhancing mass in the lower pole of the right kidney, suggestive of renal cell carcinoma.
In the present case, incidental right renal mass was detected on screening kidney ultrasonography and AP CT. Right partial nephrectomy was performed, and the diagnosis was papillary renal cell carcinoma. The diagnosis of Birt-Hogg-Dube(BHD) syndrome was confirmed by heterozygosis mutations in exon 11 of the folliculin (FLCN) gene.
- Brief Review
- Birt-Hogg Dube (BHD) syndrome, initially described in 1977, is an uncommon autosomal dominant disorder characterized by the presence of skin fibrofolliculomas, pulmonary cysts, and renal cancer. This condition is caused by germline mutations in the FLCN (folliculin) gene, which is located on chromosome 17p11.2 and encodes folliculin; the function of this protein is largely unknown, although FLCN has been linked to the mTOR pathway.
Radiologically, more than 80% of adult patients with BHD had multiple lung cysts, most often located in the lower, peripheral lung regions and along the mediastinum. The shape and size of cysts are variable. Cysts are predominantly located in the lower medial lung zone, and large cysts have a lobulated, multiseptated appearance, particularly those in the lower lungs. Cysts abutting proximal portions of lower pulmonary arteries or veins may also exist.
The histology of pleuropulmonary lesions in BHD is consistent with emphysematous changes. Despite the presence of multiple lung cysts, lung function is usually unaffected. Due to the propensity of cysts to rupture, affected individuals are predisposed to spontaneous pneumothorax (estimated 50-fold higher risk of pneumothorax than in the general population) with a high recurrence rate, approximately 80% with an average number of 3.6 episodes. The mean age of occurrence of the first episode of pneumothorax was between 30-40 years of age.
Differential diagnosis of cystic lung disease includes lymphangioleiomyomatosis (LAM), lymphocytic interstitial pneumonia (LIP), and Langerhans cell histiocytosis (LCH). LAM, which may be associated with tuberous sclerosis, shows diffuse uniform thin-walled cysts in comparison with lung cysts in BHD. LIP, which may be associated with Sjogren’s syndrome or lymphoproliferative disorders, tends to have perivascular cysts in combination with ground-glass opacity. LCH, which is usually presented in smokers, has early centrilobular nodules sparing the costophrenic angle.
- References
- 1. Lee, J. H., Jeon, M. J., Song, J. S., Chae, E. J., Choi, J. H., Kim, G. H., & Song, J. W. (2019). Birt-Hogg-Dube syndrome in Korean: clinicoradiologic features and long term follow-up. The Korean journal of internal medicine, 34(4), 830.
2. Menko, F. H., Van Steensel, M. A., Giraud, S., Friis-Hansen, L., Richard, S., Ungari, S., ... & European BHD Consortium. (2009). Birt-Hogg-Dubé syndrome: diagnosis and management. The lancet oncology, 10(12), 1199-1206.
3. Daccord, C., Good, J. M., Morren, M. A., Bonny, O., Hohl, D., & Lazor, R. (2020). Birt–hogg–dubé syndrome. European Respiratory Review, 29(157).
4. Lee, K. C., Kang, E. Y., Yong, H. S., Kim, C., Lee, K. Y., Hwang, S. H., & Oh, Y. W. (2019). A stepwise diagnostic approach to cystic lung diseases for radiologists. Korean journal of radiology, 20(9), 1368-1380.
- Please refer to
- Case 699 Case 910
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- Keywords