Neta Loewenthal

Varied clinical presentations of seven patients with mutations in CYP11A1 encoding the cholesterol side-chain cleavage enzyme, P450scc.

CONTEXT The cholesterol side-chain cleavage enzyme P450scc, encoded by CYP11A1, converts cholesterol to pregnenolone to initiate steroidogenesis. P450scc deficiency can disrupt adrenal and gonadal steroidogenesis, resembling congenital lipoid adrenal hyperplasia clinically and hormonally; only 12 such patients have been reported previously. OBJECTIVE We sought to expand clinical and genetic experience with P450scc deficiency. PATIENTS AND METHODS We sequenced candidate genes in 7 children with adrenal insufficiency who lacked disordered sexual development. P450scc missense mutations were recreated in the F2 vector, which expresses the fusion protein P450scc-Ferredoxin Reductase-Ferredoxin. COS-1 cells were transfected, production of pregnenolone was assayed, and apparent kinetic parameters were calculated. Previously described P450scc mutants were assayed in parallel. RESULTS Four of five Bedouin children in one kindred were compound heterozygotes for mutations c.694C>T (Arg232Stop) and c.644T>C (Phe215Ser). Single-nucleotide polymorphism analysis confirmed segregation of these mutations. The fifth kindred member and another Bedouin patient presented in infancy and were homozygous for Arg232Stop. A patient from Fiji presenting in infancy was homozygous for c.358T>C (Arg120Stop). All mutations are novel. As assayed in the F2 fusion protein, P450scc Phe215Ser retained 2.5% of wild-type activity; previously described mutants Leu141Trp and Ala269Val had 2.6% and 12% of wild-type activity, respectively, and Val415Glu and c.835delA lacked detectable activity. CONCLUSIONS Although P450scc is required to produce placental progesterone required to maintain pregnancy, severe mutations in P450scc are compatible with term gestation; milder P450scc mutations may present later without disordered sexual development. Enlarged adrenals usually distinguish steroidogenic acute regulatory protein deficiency from P450scc deficiency, but only DNA sequencing is definitive.

The utility of basal serum LH in prediction of central precocious puberty in girls

OBJECTIVE The mainstay of distinction between prepubertal girls and girls who are suspected of having central precocious puberty (CPP) is based on gonadotropin measurements after a GnRH stimulation test to evaluate hypothalamic-pituitary-gonadal axis maturity. The objective of this study was to determine whether a single basal gonadotropin measurement carries a useful predictive value in verifying or refuting the diagnosis of CPP. DESIGN AND METHODS Basal serum LH and FSH were measured by a chemiluminescent immunometric assay in a cohort of girls who had been evaluated for CPP before and after GnRH stimulation test. Peak LH levels higher than 5 IU/l were considered a pubertal response. RESULTS Eighty girls with suspected breast development before 8 years of age were enrolled to the study, out of whom 42 had CPP. Low basal serum LH (≤0.1 IU/l) was sufficient to rule out the diagnosis of CPP in 94.7% of the 38 prepubertal girls; the sensitivity of basal LH levels for this purpose was only 64%. The basal FSH and the basal LH to FSH ratio achieved less efficient predictive value with 76 and 71% sensitivity and 73 and 86% specificity respectively. CONCLUSION A single basal LH measurement may be adequate to confirm but not to refute the presence of CPP in most of the girls who are evaluated for early pubertal signs.

Nerve Growth Factor-Tyrosine Kinase A Pathway Is Involved in Thermoregulation and Adaptation to Stress: Studies on Patients with Hereditary Sensory and Autonomic Neuropathy Type IV

Hereditary sensory and autonomic neuropathy type IV (HSAN IV) is caused by mutations in the tyrosin kinase A (TrkA) gene, encoding for the high-affinity receptor of nerve growth factor (NGF). The NGF-TrkA system is expressed in many endocrine glands. We hypothesized that HSAN IV represents a natural model for impaired NGF effect on the neuroendocrine system in humans. We have documented the clinical outcome of 31 HSAN IV patients in a single medical center, and investigated their basal endocrine system status. The endocrine system response to thirst was compared between six patients and six healthy children. High rates of mortality (22%) and severe morbidity (30%) have been found in HSAN IV patients. Hypothermia was noted in 40% of the patients and unexplained fever was observed in 56%. Subnormal adrenal function was demonstrated in six (30%) of the patients studied. Furthermore, we found lower plasma norepinephrine (NE) levels in six HSAN IV patients compared with a control group after the thirst test. Our findings emphasize the importance of NGF-TrkA pathway in the physiology of the neuroendocrine system and its response to stress. Inadequate response to stress might contribute to the observed significant mortality, morbidity, and temperature instability in HSAN IV patients.

Phosphoglucomutase-1 deficiency: Intrafamilial clinical variability and common secondary adrenal insufficiency

Phosphoglucomutase 1 (PGM1, EC 5.4.2.2) plays a critical role in glucose homeostasis and is also essential for protein N‐glycosylation. The main clinical manifestations of PGM1 deficiency (MIM 614921) reported in 19 patients from different ethnic backgrounds include the following: cleft uvula/palate, Pierre Robin sequence, muscle weakness, dilated cardiomyopathy, growth retardation, elevated serum transaminases, hypoglycemia, and various endocrine abnormalities. We report the variable clinical picture of seven patients with PGM1 deficiency from a consanguineous family. Medical records of the patients were reviewed for clinical details and endocrine evaluation. Whole exome sequencing (WES) was performed. Seven patients aged 2–29 years were included, one patient died at 13 years old when getting off the school bus. All patients have an abnormal palatine structure (cleft palate, bifid uvula) and elevated serum transaminases, 4/7 have short stature (<−2 SDS) and one was diagnosed with growth hormone deficiency. Recurrent episodes of ketotic hypoglycemia were present in 6/7 patients. In two patients, hypoglycemic episodes have spontaneously resolved later on. Four out of seven patients have deteriorating adrenal function with abnormally low cortisol and ACTH levels during hypoglycemia and subnormal response of cortisol to low dose ACTH test . Serum electrolytes were within normal range. Hydrocortisone replacement therapy improved, but not entirely eliminated hypoglycemic episodes. WES revealed a previously described homozygous mutation c.112A>T, p.Asn38Tyr in the PGM1 gene. The clinical picture of PGM1 deficiency is variable among patients with the same mutation and genetic background. ACTH deficiency should be considered in any PGM1 deficient patient with hypoglycemia.

Natural History and Clinical Manifestations of Hyponatremia and Hyperchlorhidrosis due to Carbonic Anhydrase XII Deficiency

Introduction: We identified patients of Bedouin origin with a mutation in carbonic anhydrase XII (CA XII) leading to hyponatremia due to excessive salt loss via sweat. Methods: The medical records of patients were reviewed for clinical and laboratory data. Results: A total of 11 subjects were identified; 7 symptomatic patients presented with hyponatremic dehydration in infancy. Screening of the entire kindred identified 4 asymptomatic individuals with elevated sweat chloride. All symptomatic patients had failure to thrive and moderate-severe hyponatremia (106-124 mmol·l-1); 6 had hypochloremia (79-94 mmol·l-1). All asymptomatic subjects had normal or near-normal serum sodium and chloride concentrations. Both symptomatic and asymptomatic subjects had normal renal functions and normal cortisol response on low-dose ACTH test. All symptomatic patients were treated by dietary salt, which prevents episodes of hyponatremic dehydration and promotes growth. At follow-up, the chief complaints remained heat intolerance, accumulation of salt precipitates on the face and hyperhidrosis. No evidence for chronic renal, respiratory, gastrointestinal or fertility abnormalities was found. Conclusion: Recognizing this newly described entity and differentiating it from cystic fibrosis and pseudohypoaldosteronism are important. Patients with CA XII mutations should be followed even after early childhood, especially in hot temperatures and intense physical activity.

Essential role of carbonic anhydrase XII in secretory gland fluid and HCO3− secretion revealed by disease causing human mutation

Fluid and HCO3− secretion is essential for all epithelia; aberrant secretion is associated with several diseases. Carbonic anhydrase XII (CA12) is the key carbonic anhydrase in epithelial fluid and HCO3− secretion and works by activating the ductal Cl−–HCO3− exchanger AE2. Delivery of CA12 to salivary glands increases salivation in mice and of the human mutation CA12(E143K) markedly inhibits it. The human mutation CA12(E143K) causes disease due to aberrant CA12 glycosylation, and misfolding resulting in loss of AE2 activity.

Decreased first phase insulin response in children with congenital insensitivity to pain with anhidrosis.

Nerve growth factor (NGF) and its receptor tyrosine kinase A (TrkA) participate in endocrine pancreas morphogenesis and insulin secretion in vitro. Mutations in the TrkA gene cause the syndrome of congenital insensitivity to pain with anhydrosis (CIPA). We hypothesized that CIPA may represent a natural model for impaired NGF effect on insulin secretion in humans. Glucose challenge tests were performed in seven children with CIPA. We calculated the first phase insulin response (FPIR), the second phase insulin response (SPIR) and glucose disposal rate. FPIR was impaired in four and borderline in two patients. SPIR and glucose disposal rate were within the normal range. Oral glucose tolerance test was normal in all patients. Low FPIR in. CIPA suggests for the first time that the NGF-TrkA pathway may play a role in insulin secretion in response to glucose challenge in humans. Additional studies on the clinical significance of NGF-TrkA effects on insulin secretion are required.

Testicular expressed genes are missing in familial X-Linked Kallmann syndrome due to two large different deletions in daughter's X chromosomes.

Background: X-linked Kallmann syndrome (KS) is caused mainly by point mutations, in the KAL1 gene. Large deletions >1 Mb are rare events in the human population and commonly result in contiguous gene syndromes. Methods: A search for the mutation causing KS carried out on two pairs of first-degree cousins of 2 sisters. Results: Two different apparently independent deletions were found. The deleted sequences encompass the KAL1 gene and four known additional genes exclusively expressed in testis. Two of these genes belong to the FAM9 gene family, which shares some homology with the SCYP3 gene, previously implicated in azoospermia. One of the events causing the deletion may have been mediated by an L1 transposition, the other by a non-homologous end joining. Such non-homologous recombinations have not yet been reported in the KAL genomic region and thus this area may be more prone to deletions than previously expected. Conclusions: This is the first report on genetic characterization of KS with a deletion of solely testis-expressed genes. The absence of these genes may have unfavorable implications for the patients regarding future fertility.

Combined adrenal failure and testicular adrenal rest tumor in a patient with nicotinamide nucleotide transhydrogenase deficiency

Abstract Objective: The nicotinamide nucleotide transhydrogenase (NNT) enzyme is the main generator of nicotinamide adenine dinucleotide phosphate-oxidase in the mitochondrion. Mutations of the NNT gene have been recently implicated in familial glucocorticoid deficiency. We describe the long-term clinical course of a NNT-deficient 20-year-old patient with combined adrenal failure who had developed a testicular adrenal rest tumor and precocious puberty. Methods: The patient’s medical records were reviewed. Whole-exome sequencing was performed on DNA obtained from the patient and family members. Results: The patient experienced Addisonian crisis at 10 months of age. Enlarged testicular volume and precocious puberty, accompanied by increased testosterone levels, were noted at 6 years. Testicular biopsy revealed a adrenal rest tumor, which regressed after intensification of glucocorticoid treatment. Genetic studies disclosed a c.1163A>C, p.Tyr388Ser substitution on the NNT gene. This mutation is predicted to be damaging to NNT function. Conclusion: We demonstrated for the first time that the clinical spectrum of NNT deficiency may consist of mineralocorticoid deficiency and testicular involvement as well.

Exertional rhabdomyolysis in carbonic anhydrase 12 deficiency

Abstract Background: Carbonic anhydrase 12 (CA12) deficiency, a newly recognized rare disorder, has been described among Israeli Bedouin kindred as an autosomal recessive form of isolated salt wasting in sweat, which leads to severe infantile hyponatremic dehydration, visible salt precipitation after sweating, poor feeding and slow weight gain in infancy. Case presentation: We present two adolescents diagnosed with CA12 deficiency who developed severe rhabdomyolysis as a result of physical activity in a hot climate. Conclusions: This presentation highlights a previously unreported but significant clinical complication of this disorder and emphasizes the persistent risk of excessive salt loss via sweat and a need for certain precautions, such as increased salt intake and avoidance of prolonged and/or strenuous exercise.