CASE 14497 Published on 16.02.2017

Birt-Hogg-Dubé syndrome

Section

Chest imaging

Case Type

Clinical Cases

Authors

Stockman Arnaud, MD, De Wever Walter, MD PhD

Moorslede, Belgium;
Email:arnaudstockman@hotmail.com
Patient

47 years, male

Categories
Area of Interest Thorax, Kidney, Spleen ; Imaging Technique CT
Clinical History
A 47-year-old male patient presented with recurrent pneumothorax and a solid lesion in the upper part of the right kidney, suggestive for a renal cell carcinoma. A partial nephrectomy of the right kidney was performed. Histopathology confirmed a chromophobe renal cell carcinoma. He has fibrofolliculomas on the face and neck.
Imaging Findings
A Computed Tomography (CT) of the chest revealed several cysts along the right major fissure, bibasal subpleural in the lower lobes of both lungs and paramediastinal in the left lung. Bilateral pleural thickening was seen. A contrast-enhanced CT of the abdomen showed several cysts in the left kidney and two small cysts in the upper pole of the spleen. There was no presence of thoracic or abdominal lymphadenopathies.
Discussion
Birt-Hogg-Dubé syndrome, initially described in 1977, is a rare autosomal-dominant disorder characterized clinically by skin fibrofolliculomas, renal tumours, pulmonary cysts and spontaneous pneumothorax. Fibrofolliculomas are benign hamartomatous tumours of hair follicles and present clinically as multiple small, dome-shaped, whitish papules mainly on the nose, cheeks and the neck [1]. The renal tumours can range from benign oncocytomas to renal cell carcinomas. Benign renal cysts have been documented in patients with BHD. More than 80% of the adult patients with BHD have multiple lung cysts, often lentiform and subpleural in distribution and typically found in the basal regions of both lungs [1]. Spontaneous pneumothorax may be seen in 24% of the patients [2].

BHD syndrome is caused by mutations in the folliculin gene (FLCN), which is localized on the short arm of chromosome 17 (17p11.2) [3]. The FLCN gene encodes folliculin, a tumour suppressor protein, whose function is largely unknown. FLCN mutation analysis should be considered if patients have unexplained cystic lung disease, pneumothorax or familial renal cancer. The mutation detection rate is around 88% in a study of 58 families [4]. Counselling at-risk family members is indicated. With regard to this case, DNA analysis confirms the diagnosis of BHD.

The diagnosis is complicated by the clinical heterogeneity. Affected individuals can have inconspicuous fibrofolliculomas or even no skin manifestations at all. This patient had fibrofolliculomas on the face and neck, confirmed by dermatology. In addition, patients have an increased risk of developing a wide range of renal neoplasms from benign oncocytomas to renal cell carcinomas. The pulmonary cysts and the renal tumours can be detected by computed tomography. The localization, the shape and the distribution of the cysts on CT are important in the differentiation between Birt-Hogg-Dubé syndrome and other cystic lung diseases [5].

The treatment of skin fibrofolliculomas consist of excision or shave and cautery. Recurrent pneumothorax can be treated with talcage. Quitting smoking is strongly recommended as it increases the risk of spontaneous pneumothorax and kidney cancer [1]. The current approach for renal lesions in the context of BHD is to perform nephron sparing surgery when possible. Annual screening of affected patients or those at risk is strongly recommended starting in the fourth decade of life [6]. MRI is the best surveillance method due to high sensitivity without radiation exposure. Ultrasonography can also be used, but it has a low sensitivity for small lesions [1].
Differential Diagnosis List
Birt-Hogg-Dubé syndrome
Langerhans cell histiocytosis
Lymphangioleiomyomatosis
Lymphocytic interstitial pneumonia
Final Diagnosis
Birt-Hogg-Dubé syndrome
Case information
URL: https://eurorad.org/case/14497
DOI: 10.1594/EURORAD/CASE.14497
ISSN: 1563-4086
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