The differential diagnosis of multiple cysts in the lung includes emphysema, with or without alpha-1-antitrypsin deficiency, lymphangioleiomyomatosis (LAM), tuberous sclerosis and several rare diseases. BHD syndrome is an uncommon genetic disorder that is associated with development of multiple lung cysts, spontaneous pneumothoraces, skin lesions and renal cancers. Identification of this disorder as the cause of pulmonary disease is important because affected individuals need to be screened for renal cancer. We report a case of BHD to familiarize chest physicians with the syndrome.
A previously healthy 62-year-old woman presented with gross hematuria and was found to have large solid lesions in both kidneys. Bilateral fine needle aspirates showed chromophobe renal cell carcinomas. Multiple lung cysts were detected on chest CT. She was a non smoker with no history of respiratory illness or dyspnea. Her family history was significant for a sister with bilateral renal chromophobe tumors S/P bilateral nephrectomies at age 58, requiring chronic dialysis. She also had asymptomatic lung cysts. Her brother had a renal cell carcinoma at age 41and a maternal aunt and paternal cousin were also diagnosed with renal cancers. There was no family history of spontaneous pneumothorax. On physical examination the patient appeared well with normal vital signs and lung exam. She had multiple facial papular lesions consistent with fibrofolliculomas. CT scan of the chest showed multiple cysts throughout the lungs. Pulmonary function tests showed moderate combined restrictive and obstructive ventilatory defects. TLC was 63% predicted, FEV1 63% predicted, FEV1/FVC 71%, and DLCO 76% predicted. ABGs at rest and exercise were normal. The patient underwent genetic counseling and her slow growing tumors are under observation as she was reluctant to undergo bilateral nephrectomies at the present time.
BHD syndrome is a hereditary syndrome characterized by cutaneous hair follicle tumors, renal neoplasia, lung cysts and spontaneous pneumothorax. All features are not always present. The syndrome follows an autosomal dominant pattern with children and siblings of an affected individual having a 50% chance of inheriting the mutation. The skin lesions, when present, are asymptomatic white or skin-colored papules around the face and neck, usually appearing in the third or fourth decade. The odds ratio, adjusted for age, in BHD patients to develop renal cancer is 6.9; the kidney cancers tend to be bilateral or multifocal and are often chromophobe tumors, which are rare tumors in the general population. Cystic lung lesions have been found in approximately 80% of affected BHD patients and the odds ratio for occurrence of spontaneous pneumothorax in those with the syndrome is 50. In spite of radiographic similarities to LAM, progression to respiratory failure has not been reported and lung findings may be asymptomatic unless a pneumothorax occurs. Recent genome linkage studies have mapped BHD to chromosome 17p11.2 with expression of a defective protein “folliculin”. Genetic testing is not yet available.
In patients with unexplained lung cysts and/or pneumothorax, the possibility of BHD should be considered and appropriate family history obtained. In those affected by BHD, annual abdominal CT or other imaging techniques for screening for renal tumors is recommended as well as genetic counseling of the patient and family. Awareness of this syndrome may avoid delay in diagnosis of renal cancer.
S. Bures, None.