Renal artery stenosis due to neurofibromatosis type 1: case report and literature review

Vascular Abnormalities and Neurofibromatosis Type 1: A Paediatric Case Series

Neurofibromatosis type 1 (NF1) is a multisystemic neurocutaneous disease caused by a heterozygous mutation of the NF1 gene that encodes neurofibromin. Complications include vascular and neurologic abnormalities such as moyamoya syndrome, a cerebrovascular disorder with progressive occlusion of the large intracranial arteries, leading to ischemic events and the formation of abnormal vascular networks. Stenosis of the renal artery is another frequent complication of neurofibromatosis type 1, and it represents the most common cause of secondary hypertension in these patients. The purpose of the article is to describe the clinical manifestations of neurofibromatosis type 1 vasculopathy in 4 patients presenting with a wide range of neurologic and reno-vascular manifestations, as well as to examine current diagnostic management and follow-up, current therapeutic options, and to discuss further perspectives in terms of screening, diagnosis, and treatment.

SEVERE RETINAL ISCHEMIA IN INFANT WITH NEUROFIBROMATOSIS TYPE 1

PURPOSE

To report a case of severe retinal ischemia in an infant with neurofibromatosis type 1.

METHODS

Chart review, analysis of imaging studies, and review of literature.

RESULTS

A boy born at 37 weeks postmenstrual age with neurofibromatosis type 1 was noted to have a large plexiform neurofibroma with left-sided involvement of the cavernous sinus, internal carotid artery, orbit, and optic nerve. He was managed for left eye glaucoma with anti-hypertensive eye drops, and at 8 months of age, he was referred for retinal evaluation. Fluorescein angiography showed striking nonperfusion of the left retina with only a small area of perfused vessels in the posterior pole. A large frond of neovascularization extended anteriorly from the posterior pole. The right eye had a crescent of retinal nonperfusion in the far periphery but otherwise normal retinal vessels.

CONCLUSION

This case demonstrates a severe form of retinal ischemia in the setting of a large neurofibroma because of neurofibromatosis type 1. We hypothesize that vascular compression from the tumor led to disruption of the neurovascular bundle with resultant severe nonperfusion, neovascularization, and retinal maldevelopment.

Improved renal function in neurofibromatosis type 1 patients

Neurofibromatosis type 1 (NF1), or von Recklinghausen disease, is an autosomal dominant disease that presents with various symptoms, including café‐au‐lait spots and neurofibromas. NF1 patients occasionally suffer from renal artery vasculopathy, which impairs renal function, while results of a previous report suggested that male NF1 patients have a low creatinine level in peripheral blood. The assessment of renal function in NF1 patients remains inadequate. In this study, renal function in NF1 was assessed. We recruited 308 patients consisting of 149 NF1 patients (77 males and 72 females) and 159 control patients (102 males and 57 females). Creatinine, blood urea nitrogen and haemoglobin A1c in peripheral blood as well as protein, occult blood and sugar in urine were examined. In addition, the estimated glomerular filtration rate was calculated. The mean age and body mass index did not differ significantly between the NF1 patients and controls for both sexes. For both sexes, i) the mean creatinine value was significantly lower in the NF1 patients than in the controls; ii) the mean blood urea nitrogen value did not differ significantly between the NF1 patients and controls; iii) the mean blood urea nitrogen‐to‐creatinine ratio was significantly higher in the NF1 patients than in the controls; iv) the mean estimated glomerular filtration rate was significantly higher in the NF1 patients than in the controls; and v) the mean haemoglobin A1c value was significantly lower in the NF1 patients than in the controls. In conclusion, NF1 patients may have improved renal function. The clinical significances should be further examined.

Renal manifestations in children with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is an autosomal-dominant neurocutaneous syndrome affecting various parts of the body, including the renovascular and urinary systems. We evaluated the renovascular, urinary, glomerular, and tubular functions of children with NF1. We compared blood pressures, urinary findings, and renal glomerular and tubular functions in children with NF1 with those of a healthy age- and gender-matched control group. We evaluated 46 NF1 patients and 33 healthy controls. The mean ages of the NF1 group (female/male: 20/26) and the control group (female/male: 15/18) were 10.1 ± 4.6 and 10.6 ± 4.3 years respectively. Six NF1 patients were hypertensive. The mean blood pressures of the NF1 group were significantly higher than those of the control group. Renal artery stenosis was detected in one NF1 patient. Urinary tract anomalies were evident in 21.7% of NF1 but only 9% of control subjects. The mean estimated glomerular filtration rate (eGFR) of the NF1 group was significantly lower than that of the control group. Six NF1 patients evidenced eGFRs < 90 mL/min. In the NF1 group, tubular phosphorus reabsorption was significantly lower and uric acid excretion significantly higher than in the control group.Conclusion: Hypertension, urinary tract anomalies, and impaired renal function were more common in NF1 patients than healthy controls. Regular blood pressure measurements and evaluation of urinary tract and kidney function are essential for NF1 patients. What is Known: • NF1 is most commonly associated with systemic hypertension due to renal artery vasculopathy and the development of a pheochromocytoma. • Hydronephrosis and bladder involvement have been documented in NF1. What is New: • Renal glomerular and tubular functions may be affected in NF1.

Severe Hypertension Leading to Hemorrhagic Stroke in Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF-1), also known as von Recklinghausen’s disease, is an autosomal dominant multisystem genetic disorder affecting one in 2,600 individuals. It is caused by a mutation of the NF-1 gene located on chromosome 17q11.2. It is characterized by various cutaneous findings, including cafe-au-lait spots and axillary freckling. Hypertension is a commonly reported finding in adult patients with NF-1 but may also develop during childhood. In most cases, hypertension in NF-1 patients is primary in nature; however, secondary hypertension has been more frequently reported in NF-1 patients due to the association of NF-1 with an increased incidence of pheochromocytomas, bilateral renal artery stenosis, and coarctation of the abdominal aorta. This case reports the consequences of uncontrolled hypertension in a 23-year-old female with NF-1, illustrating the importance of screening for hypertension in children diagnosed with NF-1, and emphasizing the higher incidence of both primary and secondary causes of hypertension in the NF-1 patient population. In this case, no secondary causes of hypertension were found; therefore, a diagnosis of primary hypertension was made and the appropriate therapy was initiated to prevent further complications.

Imaging Features of Neurofibromatosis Type 1 in the Abdomen and Pelvis

OBJECTIVE. Loss of the neurofibromatosis type 1 (NF1) tumor suppressor protein causes uninhibited activation of the RAS oncogene, which leads to tumorigenesis in patients with NF1. This case-based review discusses imaging manifestations of NF1 in the abdomen and pelvis, highlighting key genetic associations and management to elucidate features different from the general population. CONCLUSION. The spectrum of pathologic findings includes gastrointestinal tumors such as gastrointestinal stromal tumors, genitourinary lesions including urogenital neurofibromas, vascular entities such as renal artery stenosis, and less common associations like lymphoma.

Diagnosis and clinical course of ocular ischemic syndrome with retinal vascular abnormalities due to unilateral ocular artery and internal carotid artery stenosis in a child with neurofibromatosis type 1: a case report

Background

Neurofibromatosis type 1 (NF1) is a hereditary disease that causes neurofibromas generally, but it has been reported to sometimes be associated with various forms of blood vessel stenosis, occlusion and vascular abnormalities of unknown mechanism. However, a symptomatic case with simultaneous ophthalmic artery stenosis and internal carotid artery stenosis is an extremely rare pathogenesis in a child with NF1. In this report, we performed the diagnosis and observation using various imaging modalities for this rare pediatric case.

Case presentation

A 6-year-old girl diagnosed with NF1 presented with gradual visual loss in the right eye. Best corrected visual acuity (BCVA) was 20/40 OD and the intraocular pressure (IOP) was normal in both eyes. Retinal vascular abnormalities with tortuous vessels and optic disc pallor were observed in the right fundus. Widefield fluorescein angiography revealed multiple sites of neovascularization and a large non-perfusion area in the peripheral retina. Optical coherence tomography angiography showed retinal vascular abnormalities in the right eye and revealed differences in inner retinal thickness and blood flow signal between the left and right eyes. Laser speckle flowgraphy showed that chorioretinal blood flow was significantly decreased in the right eye. Cerebral angiography revealed the right ophthalmic artery was significantly narrowed throughout. In addition, Magnetic resonance angiography revealed that the right internal carotid artery was significantly narrowed in the ophthalmic segment. We diagnosed ophthalmic artery and internal carotid artery stenosis with retinal vascular abnormalities and ocular ischemic syndrome in NF1. Because IOP increased to 35 mmHg, due to neovascular glaucoma in addition to mild vitreous hemorrhage occurred, panretinal photocoagulation was performed after intravitreal bevacizumab injection. After treatments, IOP normalized, but BCVA decreased to 20/100 OD. Arterial spin labeling showed normal cerebral blood flow. The patient is currently being carefully monitored.

Conclusions

We have described the diagnosis and treatment of ocular ischemic syndrome due to multiple arteries stenosis in a child with NF 1. Utilization of various imaging modalities was helpful in diagnosing the complicated pathogenesis. However, since direct intervention by neurosurgery is not possible in this case, it is expected that treatment will be extremely difficult in the future.

Genetics of renovascular hypertension in children

OBJECTIVE

In most cases of renovascular hypertension in children, the cause is unclear. The aim of this study was to investigate genetic variation as a factor in the development of renovascular hypertension in children.

METHODS

In a cohort of 37 unrelated children from a single tertiary referral center, exome sequencing was performed. We assessed variants in recognized and suspected disease genes and searched for novel ones with a gene-based variant-burden analysis.

RESULTS

In the majority of patients, exome sequencing could not identify causative variants. We found a pathogenic variant in a recognized associated disease gene in five patients (three pathogenic variants in NF1, one in ELN and a deletion of chromosome 7q11.23, consistent with Williams syndrome). In two other patients, (likely) pathogenic variants were found in putative renovascular hypertension genes (SMAD6 and GLA), with clinical implications for both. Ten additional patients carried variants of uncertain significance (VUS) in known (n = 4) or putative (n = 6) renovascular hypertension disease genes. Rare variant burden analysis yielded no further candidate genes.

CONCLUSION

Genetic contributors, such as germline mutations in NF1, ELN, 7q11.23del were present in only 5 out of 37 (14%) children with renovascular hypertension. Twelve other children (32%) had potentially causal variants identified, including a pathogenic variant in SMAD6; a vasculopathy gene hitherto unknown to link with renovascular hypertension. Most importantly, our data show that exome sequencing can rarely identify the cause of renovascular hypertension in nonsyndromic children. We suggest that nongenetic factors or somatic genetic variation will play a more important role.

Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents

These pediatric hypertension guidelines are an update to the 2004 "Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents." Significant changes in these guidelines include (1) the replacement of the term "prehypertension" with the term "elevated blood pressure," (2) new normative pediatric blood pressure (BP) tables based on normal-weight children, (3) a simplified screening table for identifying BPs needing further evaluation, (4) a simplified BP classification in adolescents ≥13 years of age that aligns with the forthcoming American Heart Association and American College of Cardiology adult BP guidelines, (5) a more limited recommendation to perform screening BP measurements only at preventive care visits, (6) streamlined recommendations on the initial evaluation and management of abnormal BPs, (7) an expanded role for ambulatory BP monitoring in the diagnosis and management of pediatric hypertension, and (8) revised recommendations on when to perform echocardiography in the evaluation of newly diagnosed hypertensive pediatric patients (generally only before medication initiation), along with a revised definition of left ventricular hypertrophy. These guidelines include 30 Key Action Statements and 27 additional recommendations derived from a comprehensive review of almost 15 000 published articles between January 2004 and July 2016. Each Key Action Statement includes level of evidence, benefit-harm relationship, and strength of recommendation. This clinical practice guideline, endorsed by the American Heart Association, is intended to foster a patient- and family-centered approach to care, reduce unnecessary and costly medical interventions, improve patient diagnoses and outcomes, support implementation, and provide direction for future research.

Revascularization in a 17-Year-Old Girl with Neurofibromatosis and Severe Hypertension Caused by Renal Artery Stenosis

Renal artery stenosis caused by neurofibromatosis is a rare cause of renovascular hypertension. This hypertension can develop during childhood and is one of the leading causes of poor outcome. We report the case of a 17-year-old girl who was incidentally diagnosed with severe hypertension. During her examination for secondary hypertension, we reached a diagnosis of neurofibromatosis type 1 on the basis of a cluster of typical findings: optic nerve glioma, café au lait spots, nodular neurofibromas, and axillary freckling. Renal angiograms revealed a hemodynamically significant left renal artery stenosis (70%). Renal angioplasty with a self-expanding stent was performed one month later for rapidly progressive renal artery stenosis (90%) and uncontrolled blood pressure. Excellent blood pressure control resulted immediately and was maintained as of the 2-year follow-up evaluation. We think that percutaneous transluminal renal angioplasty can be effective in select patients who have neurofibromatosis type 1 and refractory hypertension caused by renal artery stenosis.

[Fibromuscular dysplasia of renal arteries]

Fibromuscular dysplasia is non-atherosclerotic, non-inflammatory disease of the medium caliber arteries causing segmental stenosis, and sometimes aneurysm and/or dissection. Renal involvement is either asymptomatic or revealed by hypertension, rarely acute complications (renal infarction/hemorrhage). Cross-sectional imaging or angiography differentiates multifocal fibromuscular dysplasia (pearl necklace appearance) and focal fibromuscular dysplasia (tubular stenosis). Several differential diagnoses are to be mentioned. Carotid and vertebral involvement are possible. Smoking cessation must be encouraged. Selected patients benefit from renal revascularization. The best indications are recent or resistant hypertension, and progressive renal atrophy. Angioplasty without stent revascularization is the technique of choice in purely stenotic forms.

Clitoromegaly as first presentation of a neurocutaneous syndrome in a 3-year-old girl

A rare cause of clitoral hypertrophy in a child is neurofibromatosis type 1 (NF1). Although evaluation, including karyotype and hormonal studies, is necessary to exclude ambiguous genitalia, the diagnosis of neurofibromatosis as a possible cause of clitoromegaly may help avoid lengthy and sometimes invasive interventions.