Faculty Bibliography

Familial dysautonomia (Riley-Day syndrome, hereditary sensory and autonomic neuropathy type III) is a rare autosomal recessive disease characterized by impaired development of primary sensory and autonomic neurons resulting in a severe neurological phenotype, which includes arterial baroreflex and chemoreflex failure with high frequency of sleep-disordered breathing and sudden death during sleep. Although a rare disease, familial dysautonomia represents a unique template to study the interactions between sleep-disordered breathing and abnormal chemo- and baroreflex function. In patients with familial dysautonomia, ventilatory responses to hypercapnia are reduced, and to hypoxia are almost absent. In response to hypoxia, these patients develop paradoxical hypoventilation, hypotension, bradycardia, and potentially, death. Impaired ventilatory control due to chemoreflex failure acquires special relevance during sleep when conscious control of respiration withdraws. Overall, almost all adult (85%) and pediatric (95%) patients have some degree of sleep-disordered breathing. Obstructive apnea events are more frequent in adults, whereas central apnea events are more severe and frequent in children. The annual incidence rate of sudden death during sleep in patients with familial dysautonomia is 3.4 per 1000 person-year, compared to 0.5-1 per 1000 person-year of sudden unexpected death in epilepsy. This review summarizes recent developments in the understanding of sleep-disordered breathing in patients with familial dysautonomia, the risk factors for sudden death during sleep, and the specific interventions that could prevent it.

Hypokalemia of renal origin can arise from genetic abnormalities in a variety of transporters or channel proteins that mediate tubular handling of potassium. Recently, mutations in claudin 10 have been documented in patients with hypokalemia in association with a range of other electrolyte abnormalities and skin and sweat gland manifestations. We report a 12-year-old Hispanic boy who presented with anhydrosis, aptyalism, alacrima, hypokalemia, and hypocalciuria, in whom we detected a homozygous mutation in the claudin 10 gene. During the 4-year follow-up period, he developed hypermagnesemia and a decline in estimated glomerular filtration rate to 59mL/min/1.73m². His unaffected parents and siblings were heterozygous for the mutation. We summarize the clinical phenotype encountered in patients with claudin 10 mutations. It is characterized by significant heterogeneity in electrolyte and extrarenal abnormalities and is associated with a risk for progressive loss of kidney function in up to 33% of cases. Awareness of this association between claudin 10 mutations and electrolyte abnormalities, namely hypokalemia and hypermagnesemia, sheds new light on the physiology of potassium and magnesium handling along the nephron and increases the likelihood of identifying the underlying tubular mechanism in patients with newly diagnosed hypokalemia with or without concomitant hypermagnesemia.

Objective: We present the protocol, recruitment numbers, and preliminary adverse event profile of patients enrolled in a single-center phase-2 futility trial using sirolimus for multiple system atrophy (MSA) (ClinicalTrials.gov: NCT03589976).
Background(s): In patients with MSA, autophagy is impaired and misfolded aSyn accumulates in neurons and glia, causing neurodegeneration. Sirolimus, a medication that has been approved by the U.S. Food and Drug Administration for chronic treatment in humans for a variety of disorders for almost 20 years, is a potent activator of autophagy. We hypothesize that treatment with sirolimus might activate autophagy of aSyn resulting in reduced neurodegeneration and slower progression of the neurological deficits in patients with MSA.
Method(s): Single-center, randomized, placebo-controlled, phase-2 futility clinical trial to determine if sirolimus is of sufficient promise to slow the disease progression of patients with MSA, prior to embarking on a large-scale and costly phase-3 study to assess its efficacy. Non-futility will offer strong support for a phase-3 trial to detect clinical efficacy. We will enroll 56 patients with a 3:1 (sirolimus:placebo) randomization. We expect to complete enrollment in 2 years.
Result(s): The first patient was screened and enrolled in September 2018. By May 2019, 35 patients had been screened and 31 had been enrolled and randomized. By October 2019 we expect to have enrolled 43 patients (76% of our final target enrollment). Common adverse events included oral ulcers, abdominal discomfort and diarrhea/loose stools. Recruitment and adverse events will be updated by the time of this abstract presentation.
Conclusion(s): This is the first time sirolimus or analogs are being used clinically with the aim of slowing disease progression in patients with neurodegenerative disorders. Our observations may offer strong support for a phase-3 trial to confirm the efficacy of sirolimus in MSA

Background: Disease progression of multiple system atrophy (MSA) as measured by the Unified Multiple System Atrophy Rating Scale (UMSARS) varied significantly in natural history studies. Reported 1-year UMSARS-1 and UMSARS-2 progression rates ranged from 3.9 to 6.5 and 3.5 to 8.2, respectively. We hypothesize that this variability is due, at least in part, to differences in severity at enrollment and a potential ceiling effect in the scale, so that patients in more advanced stages may appear to worsen less, which would have important implications for clinical trial design.
Method(s): We analyzed the rate of change in the UMSARS in a large international cohort of well-characterized patients with a clinical diagnosis of possible or probable MSA enrolled in the Natural History Study of Synucleinopathies. Annualized progression rates were obtained using 2-year follow-up data.
Result(s): 293 patients (62.0+/-7.8 years old) with MSA were enrolled. Disease duration was 4.5+/-3.6 years. 98 patients completed 1-year evaluations and 48 completed the 2-year evaluation. The 12-month progression rates were 5.5+/-5.3 for the UMSARS-I, 6.6+/-5.2 for the UMSARS-II, and 11.9+/-9.8 for the total score. The 24-month progression rates were 10.8+/-7.1 for the UMSARS-I, 12.5+/-7.9 for the UMSARS-II, and 22.6+/-13.7 for the total score. Annualized progression rates were divided according to their baseline UMSARS-I and UMSARS II. There was a significant (p=0.0461) inverse relationship between rate of progression and UMSARS-I at baseline. A similar, but not significant trend was observed with UMSARS-II at baseline.
Conclusion(s): The rate of progression as measured by UMSARS is influenced by the baseline disease severity. A ceiling effect should be considered when planning enrollment, power calculations, and outcome measures in clinical trials

Objective: To describe an unusual case of a young girl of Jewish Ashkenazi descent with two rare genetic disorders: familial dysautonomia and congenital adrenal hyperplasia.
Method(s): Case report.
Result(s): Female patient presenting with hypotonia, failure to thrive, recurrent vomiting and frequent lower respiratory tract infections during the first year of life. Her physical exam disclosed genital ambiguity and, because an older sister had a diagnosis of congenital adrenal hyperplasia, the diagnosis was suspected in this case, and confirmed by low levels of cortisol and aldosterone. Targeted genetic testing showed homozygosis for a pathogenic variant in the CYP21A2 gene (c.293-13C[G, aka I2G, well-described in Jewish Ashkenazi patients) and heterozygosis for 7 other variants in the same gene. She was started on fludrocortisone for mineralocorticoid replacement therapy. Additional signs and symptoms were identified including frequent aspiration pneumonias prompting a gastrostomy tube placement at 6 months of age, emotionally-induced episodes of face, hand and feet blotching, frequent falls, impaired sensitivity to pain, and lack of tears. Additional genetic testing at age 2 disclosed homozygous copies of the founder mutation variant of familial dysautonomia (variant IVS20?6 T[C) in the IKBKAP gene.
Conclusion(s): The presence of one rare genetic disorder does not preclude the presence of another rare genetic disorder. Signs and symptoms not consistent with one diagnosed genetic disorder should prompt suspicion of additional causes