[Genetic diffuse cystic lung disease in adults]

Multiple cystic lung diseases comprise a wide range of various diseases, some of them of genetic origin. Lymphangioleiomyomatosis (LAM) is a disease occurring almost exclusively in women, sporadically or in association with tuberous sclerosis complex (TSC). Patients with LAM present with lymphatic complications, renal angiomyolipomas and cystic lung disease responsible for spontaneous pneumothoraces and progressive respiratory insufficiency. TSC and LAM have been ascribed to mutations in TSC1 or TSC2 genes. Patients with TSC are variably affected by cutaneous, cognitive and neuropsychiatric manifestations, epilepsy, cerebral and renal tumors, usually of benign nature. Birt-Hogg-Dubé syndrome is caused by mutations in FLCN encoding folliculin. This syndrome includes lung cysts of basal predominance, cutaneous fibrofolliculomas and various renal tumors. The main complications are spontaneous pneumothoraces and renal tumors requiring systematic screening. The mammalian target of rapamycin (mTOR) pathway is involved in the pathophysiology of TSC, sporadic LAM and Birt-Hogg-Dubé syndrome. MTOR inhibitors are used in LAM and in TSC while Birt-Hogg-Dubé syndrome does not progress towards chronic respiratory failure. Future challenges in these often under-recognized diseases include the need to reduce the delay to diagnosis, and to develop potentially curative treatments. In France, physicians can seek help from the network of reference centers for the diagnosis and management of rare pulmonary diseases.

[Tuberous sclerosis system: A review]

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that affects different organs and caused by loss-of-function mutations in one of two genes: TSC1 or TSC2. TSC1 or TSC2 gene mutation lead to dysfunction of hamartin or tuberin, respectively. Hamartin and tuberin form a protein complex that helps regulate cellular proliferation. These proteins form a complex that constitutively inhibits the mammalian target of rapamycin (mTOR) signaling pathway, leading to permanent activation of mTOR signaling within all TSC-associated lesions. Major features of TSC include tumors of the brain, skin, heart, lungs and kidneys, seizures and TSC-associated neuropsychiatric disorders, which can include autism spectrum disorder and cognitive disability. These disorders are usually diagnosed in children and adults. Specific guidelines for diagnosis, surveillance, and management have been proposed by the International Tuberous Sclerosis Complex Consensus Group. Several randomized controlled trials led to regulatory approval of the use of mTOR inhibitors for the treatment of renal angiomyolipomas, brain subependymal giant cell astrocytomas, refractory epilepsy and pulmonary lymphangioleiomyomatosis.

[Prevalence of the tuberous sclerosis complex at patients taken care for a renal angiomyolipoma]

INTRODUCTION

Bourneville's tuberous sclerosis or Tuberous Sclerosis Complex (TSC) is an autosomal dominant hereditary phakomatosis associated with angiomyolipomas (AML) of the kidney. The aim of this study was to identify the prevalence of TSC in patients diagnosed and cared for AML in our department of urology.

MATERIALS AND METHODS

All the patients with AML were included between March 2009 and June 2016 in a French university hospital. Each patient was reviewed in consultation with a clinical examination and imaging. Specific clinical criteria were used to refer patients to genetic analysis. Patients with a high TSC probability had a genetic analysis to search TSC1 and TSC2 genes mutations.

RESULTS

In all, 28 patients were included and 3 (11%) were diagnosed TSC. The median age of the patients was 62 years (36-82 years). The most frequent clinical criteria were facial angiofibromas in 7 patients (25%). Among the 8 patients (29%) with evocative clinical criteria, a mutation of the TSC1 and TSC2 genes was identified in 3 patients (11%) with a diagnosis of TSC made before the AML diagnosis.

CONCLUSION

In this study, 8 patients (29%) presented clinical criteria suggestive of TSC, preferentially dermatological. The diagnosis was confirmed by screening TSC1 and TSC2 genes mutations in 3 patients (11%), nevertheless prevalence of TSC is most probably underestimated by the genetic mosaïcisme of this pathology.

[Pulmonary lymphangioleiomyomatosis: From pathogenesis to management]

INTRODUCTION

Pulmonary lymphangioleiomyomatosis (LAM) is a rare disease affecting mainly young women.

BACKGROUND

The respiratory manifestations are characterized by a progressive cystic destruction of the lung parenchyma. Extrapulmonary involvement includes benign renal tumours called angiomyolipomas and abdominal lymphatic masses called lymphangioleiomyomas. At the pathological level, the cellular proliferation found in LAM is in part due to the presence of mutations in the tumour suppressor genes TSC1 and TSC2 (Tuberous Sclerosis Complex). These mutations lead to the activation of the mTOR pathway, which is currently the main therapeutic target. mTOR inhibitors such as sirolimus or everolimus have shown a beneficial effect on the decline in pulmonary function and a reduction of angiomyolipoma size, but are necessary in only some patients.

PERSPECTIVES

LAM cells have migratory properties mediated by the formation of new lymphatic vessels. They are also able to secrete metalloproteases, which enhance their invasiveness. Moreover, the expression of estrogen and progesterone receptors by LAM cells suggests a possible role for sex hormones in the pathogenesis of the disease.

CONCLUSION

A better understanding of mTOR-independent mechanisms would allow the development of novel therapeutic approaches.

[A cardiac rhabdomyome evoking the antenatal diagnosis of a Bourneville's tuberous sclerosis]

Rare hereditary affection, the Bourneville's tuberous sclerosis (BTS) is an autosomal dominant inherited phakomatosis. Rhabdomyomes are the most frequent cardiac tumors in children and infants, they are one of the most premature modes of revelation of the STB. They sometimes allow to envisage the diagnosis in antenatal period at the same time as the genetic and neurological explorations. We report the diagnosis of a fetal BTS evoked by the antenatal discovery of a cardiac rhabdomyome. The antenatal cerebral explorations, realized by magnetic resonance imagery (MRI), put evidence cerebral localisations confirming the diagnosis.