Measured parental height in Turner syndrome-a valuable but underused diagnostic tool.

Early diagnosis of Turner syndrome (TS) is necessary to facilitate appropriate management, including growth promotion. Not all girls with TS have overt short stature, and comparison with parental height (Ht) is needed for appropriate evaluation. We examined both the prevalence and diagnostic sensitivity of measured parental Ht in a dedicated TS clinic between 1989 and 2013. Lower end of parental target range (LTR) was calculated as mid-parental Ht (correction factor 12.5 cm minus 8.5 cm) and converted to standard deviation scores (SDS) using UK 1990 data, then compared with patient Ht SDS at first accurate measurement aged > 1 year. Information was available in 172 girls of whom 142 (82.6%) were short at first measurement. However, both parents had been measured in only 94 girls (54.6%). In 92 of these girls age at measurement was 6.93 ± 3.9 years, Ht SDS vs LTR SDS - 2.63 ± 0.94 vs - 1.77 ± 0.81 (p < 0.001), Ht SDS < LTR in 78/92 (85%). Eleven of the remaining 14 girls were < 5 years, while karyotype was 45,X/46,XX in 2 and 45,X/47,XXX in 3. CONCLUSION: This study confirms the sensitivity of evaluating height status against parental height but shows that the latter is not being consistently measured. What is Known: • Girls with Turner syndrome are short in relation to parental heights, with untreated final height approximately 20 cm below female population mean. • Measured parental height is more accurate than reported height. What is New: • In a dedicated Turner clinic, there was 85% sensitivity when comparing patient height standard deviation score at first accurate measurement beyond 1 year of age with the lower end of the parental target range standard deviation. • However, measured height in both parents had been recorded in only 54.6% of the Turner girls attending the clinic. This indicates the need to improve the quality of growth assessment in tertiary care.

Key Stages in the Development and Establishment of Paediatric Endocrinology: A Template for Future Progress.

BACKGROUND: Paediatric endocrinology became recognised in Western European countries in the 1960s and 1970s. It is now a thriving paediatric sub-speciality in many countries but remains non-existent or in its infancy in others. We have had the privilege to work in Western centres of excellence, and this review outlines the key stages in the development of modern centres, discussing the human and organisational issues that have underpinned progress in the establishment of this paediatric sub-speciality. SUMMARY: Human determination, vision, and ambition to create a modern centre and become a national flag bearer in the field are key components of success. The realisation that learning by spending time as a fellow away from one's home institution, so that knowledge can be acquired and brought back home, is also a key factor. Career structures should be designed to mentor and guide the trainee returning from a fellowship abroad. Scientific societies such as the European Society for Paediatric Endocrinology (ESPE) are key resources for networking, support, and discussion with experienced colleagues who may have faced similar challenges. Training and acquisition of knowledge through on-site or e-learning initiatives are beneficial and numerous examples exist, including the telemedicine model of store-and-forward consultations. Leadership skills can be learnt, and good working relationships with adult endocrinology colleagues result in benefits and political support. KEY MESSAGES: The development of paediatric endocrinology in a region with hitherto no such facilities constitutes a major contribution to local, regional, and, in all likelihood, national patient care.

Effect of oxandrolone and timing of pubertal induction on final height in Turner syndrome: final analysis of the UK randomised placebo-controlled trial.

The UK Turner syndrome (TS) study examined the effect on final height of oxandrolone 0.05 mg/kg/day (maximum dose 2.5 mg) versus placebo from 9 years of age; and delaying ethinylestradiol induction of puberty by 2 years from 12 (E12) to 14 (E14) years in growth hormone-treated girls with TS. The study ran from 1999 to 2013. By 2011, eighty-two of 92 participants had reached final height and an interim analysis using the Super-Imposition by Translation And Rotation model showed significant increases in final height with both oxandrolone and E14. The analysis has been repeated now that all 92 patients have reached final height. Oxandrolone still significantly increased final height by 4.1 cm (95% CI 1.6 to 6.6, n=92) compared with 4.6 cm previously. However, the E14 effect was no longer significant at 2.7 cm (95% CI -0.8 to 6.1, n=56) compared with 3.8 cm previously.

Congenital Hypothyroidism: Space-Time Clustering of Thyroid Dysgenesis Indicates a Role for Environmental Factors in Disease Etiology.

Background: The etiology of most cases of congenital hypothyroidism (CHT) due to thyroid dysgenesis (DG) is unknown. If transient environmental factors can impact on thyroid gland development, then clustering of cases in time and/or space may occur, and this would be more likely in thyroid DG than dyshormonogenesis (DHG). Methods: The newborn screening program for CHT in Scotland is linked to a central database that includes case details such as postcode. The etiology of CHT is investigated in many cases of CHT using scintigraphy and/or ultrasonography. We looked for evidence of a change in CHT incidence with year of birth and according to season of the year. We then undertook space-time clustering analysis (using a method based on K-functions, with nearest neighbor thresholds) of CHT in Scotland between 1979 and 2015. We also looked for evidence of overall changes associated with sex and area-based birth density. Results: Of 531 cases with CHT during the study period, 290 cases had been categorized as DG (n = 229) or DHG (n = 61) following more detailed investigation. The incidence of CHT increased with year of birth and was in part linked to changing methodology, but there was no seasonality. There was no evidence of overall space-time clustering (p = 0.06), but there was evidence of clustering in babies with DG (p = 0.007). This picture appeared to be most closely linked to underlying thyroid gland hypoplasia rather than thyroid gland agenesis or ectopia. There was significant space-time clustering for both males and females, but clustering was restricted to lesser birth density areas. There was also evidence of clustering for unknown cases (p < 0.001). Clustering of these cases was restricted to females but was present for cases from both greater and lesser birth density areas. There was no evidence of clustering in cases of DHG. Conclusions: These data suggest that an unidentified environmental factor or factors may be involved in the etiology of thyroid DG in Scotland. The variation in CHT incidence observed internationally may reflect environmental as well as genetic factors.

Heterogeneous tissue in the thyroid fossa on ultrasound in infants with proven thyroid ectopia on isotope scan--a diagnostic trap.

BACKGROUND: Thyroid imaging is of proven help in establishing a diagnosis of congenital hypothyroidism in infants. US often shows tissue in the thyroid fossa when radionuclide scintigraphy reveals only ectopic uptake. OBJECTIVE: Our hypothesis was that the use of US alone could lead to the mistaken diagnosis of normal or dysplastic thyroid in cases of scintigraphy-proven thyroid ectopia. MATERIALS AND METHODS: We undertook a detailed retrospective review and analysis of imaging and concurrent biochemistry in infants with thyroid ectopia, confirmed by radionuclide scintigraphy. RESULTS: Eighteen infants had thyroid ectopia; ten of the original US reports had suggested that cervical thyroid tissue was present. Review showed bilateral tissue in the thyroid fossa in all that was non-thyroidal in nature since, apart from showing no radionuclide uptake, it exhibited some or all of the following typical features: hyperechogenicity, heterogeneity, small size, poor vascularity, and anechoic and/or hypoechoic cysts. Also, extension of the tissue both around and behind the large cervical blood vessels was a universal finding. CONCLUSION: Considerable experience is required to interpret neonatal thyroid US. We caution against diagnosing a dysplastic/hypoplastic thyroid gland in situ on the basis of US alone, particularly if the tissue exhibits any of the non-thyroidal features described.

Audit of initial management of congenital hypothyroidism in the United Kingdom--comparison of UK practice with European and UK guidelines.

BACKGROUND: Prompt and adequate management of newly diagnosed congenital hypothyroidism (CH) has been shown to optimise intellectual outcome. METHODS: A questionnaire survey of the British Society for Paediatric Endocrinology and Diabetes (BSPED) membership was undertaken, examining current clinical practice in neonatal CH. Results were compared with published management guidelines from Europe and the UK. RESULTS: The response rate was 86%. The majority were largely compliant with both guidelines. 43% review newly referred infants on the day of notification. However, 26% treat severe CH with < 10 microg/kg/day thyroxine and nearly 20% do not follow up until at least 14 days after initiating treatment, in contrast to both guidelines. Despite a new liquid T4 preparation being licensed, respondents preferred tablet T4. CONCLUSION: Rapidity of assessment and adequate follow up of suspected CH is critical to outcome. Existing European and UK guidelines should be reviewed and expanded to incorporate new evidence, together with increased advice on preparation and administration of T4.

Ethinyl estradiol treatment for growth limitation in girls with Marfan's syndrome--experience from a single center.

OBJECTIVES: Tall stature, a major characteristic of Marfan's syndrome, may be of concern to the family, particularly if the patient is a girl. Experience with treatment options-sex steroid or somatostatin analogue-for height reduction in girls is limited. We have evaluated our experience of estrogen treatment in girls with Marfan's syndrome attending the pediatric endocrine clinic in Glasgow between 1989 and 2005. DESIGN AND METHODS: Retrospective case note analysis combined with ascertainment of final/near final height, comparing outcome in treated and untreated girls. Cardiovascular health was assessed by examining aortic root diameter and blood pressure. RESULTS: The study cohort comprised four treated and five untreated girls, of whom three were sisters. Treatment was started in the four girls at chronological age 10.0 (2.1) years, mean (SD) height 155.0 (9.8) cm, and Tanner breast stage B1 in three and B2 in one. Ethinyl estradiol was administered in stepwise incremental regimens, starting at 10 microg/day and reaching 100 microg/day after 10 weeks in two girls and starting at 2 microg/day and reaching a maximum of 30-50 microg/day over a 2- to 3-year period in two girls. Mean +/- SD (range) final/near final height of the four treated girls was 174.3 (2.6) (170.6-176.6) cm compared with 183.0 (6.9) (171.5-190.3) cm in the five untreated girls. No deaths occurred in the treated group while one untreated girl died from presumed arrhythmia aged 18 years. Aortic root diameter increased with age, by mean (SD) 5.0 (2.1) and 5.8 (4.5) mm in treated and untreated groups, respectively, but with no between-group differences after treatment. CONCLUSIONS: The estrogen doses used in this study are lower than in previous reports. The results, although unsuitable for statistical analysis due to small numbers, are encouraging with no adverse events being recorded. Future research should be multicenter in design.

Predicted Benign and Synonymous Variants in CYP11A1 Cause Primary Adrenal Insufficiency Through Missplicing.

Primary adrenal insufficiency (PAI) is a potentially life-threatening condition that can present with nonspecific features and can be difficult to diagnose. We undertook next generation sequencing in a cohort of children and young adults with PAI of unknown etiology from around the world and identified a heterozygous missense variant (rs6161, c.940G>A, p.Glu314Lys) in CYP11A1 in 19 individuals from 13 different families (allele frequency within undiagnosed PAI in our cohort, 0.102 vs 0.0026 in the Genome Aggregation Database; P < 0.0001). Seventeen individuals harbored a second heterozygous rare disruptive variant in CYP11A1 and two had very rare synonymous changes in trans (c.990G>A, Thr330 = ; c.1173C>T, Ser391 =). Although p.Glu314Lys is predicted to be benign and showed no loss-of-function in an Escherichia coli assay system, in silico and in vitro studies revealed that the rs6161/c.940G>A variant, plus the c.990G>A and c.1173C>T changes, affected splicing and that p.Glu314Lys produces a nonfunctional protein in mammalian cells. Taken together, these findings show that compound heterozygosity involving a relatively common and predicted "benign" variant in CYP11A1 is a major contributor to PAI of unknown etiology, especially in European populations. These observations have implications for personalized management and demonstrate how variants that might be overlooked in standard analyses can be pathogenic when combined with other very rare disruptive changes.

Hashimoto's thyroiditis in Down's syndrome: clinical presentation and evolution.

AIM: It was the aim of this study to describe the presentation and clinical course of Hashimoto's thyroiditis (HT) in children with Down's syndrome (DS) in 2 Scottish health regions. PATIENTS AND METHODS: We retrospectively analysed clinical, biochemical and thyroid antibody status in 38 patients with DS with HT diagnosed from 1989 to 2004. RESULTS: The sex distribution was similar (20 males, 18 females), with a median age of 12.3 years (range 2.1-17.7). Of the 38 patients reviewed, 29 were identified by screening. A goitre was present in 6/38 patients. Thyroid antibodies were positive in 36/38 patients, negative in 1/38, and data were unavailable for 1/38. At presentation, 37/38 patients were hypothyroid: 21/37 with compensated hypothyroidism (6 treated initially) and 16/37 with decompensated hypothyroidism (all treated). Of the 15/21 compensated patients who were untreated initially, only 3 remitted while 12 showed disease progression prompting treatment. In the decompensated group, 1/16 patient pursued a fluctuating course between hypo- and hyperthyroidism. The final patient, who was hyperthyroid at presentation, also showed marked fluctuation in thyroid function over a 5-year period. CONCLUSION: The natural history of HT in DS is unusual, with no female predominance and infrequent goitre in our cohort. While almost all patients required treatment eventually, clinicians should be aware that the disease may pursue a fluctuating course between hypo- and hyperthyroidism.

Long-term outcome of thyrotoxicosis in childhood and adolescence in the west of Scotland: the case for long-term antithyroid treatment and the importance of initial counselling.

BACKGROUND: Thyrotoxicosis is both rarer and more severe in children than in adults, rendering management difficult and often unsatisfactory. OBJECTIVE: To ascertain outcome in a geographically defined area of Scotland between 1989 and 2014. METHOD: Retrospective case note review with follow-up questionnaire to family doctors for patients with Graves' disease and Hashimoto's thyroiditis. RESULTS: Sixty-six patients (58 females:8 males) comprising 53 with Graves' disease and 13 with Hashimoto's thyroiditis were diagnosed at median 10.4 (2.9-15.8) years and followed up for 11.8 (2.6-30.2) years. Antithyroid drug (ATD) therapy was stopped electively in 35 patients after 4.5 (1.5-8.6) years, resulting in remission in 10/13 Hashimoto's thyroiditis and 10/22 Graves' disease. Side effects occurred in 12 patients receiving carbimazole, six of whom changed to propylthiouracil; no adverse events occurred in the latter patients.Second-line therapy was given to 37 patients (34 with Graves' disease), comprising radioiodine (22) at 15.6 (9.3-24.4) years for relapse (6), poor control/adherence (14) or electively (2); and surgery (16) at 12 (6.4-21.3) years for relapse (4), poor control/adherence (5) and electively (7). Adherence problems with thyroxine replacement were reported in 10/33 patients in adulthood. CONCLUSIONS: Hashimoto's thyroiditis should be distinguished from Graves' disease at diagnosis since the prognosis for remission is better. Remission rates for Graves' disease are low (10/53 patients), time to remission variable and adherence with both ATD and thyroxine replacement often problematic. We recommend (a) the giving of long-term ATD rather than a fixed course of treatment in GD and (b) meticulous and realistic counselling of families from the time of diagnosis onwards.

A novel missense mutation in DAX-1 with an unusual presentation of X-linked adrenal hypoplasia congenita.

A male presented at age 2.2 years with a 6-week history of intermittent vomiting and hyperpigmentation. Investigations showed salt wasting with hyperkalaemia, a grossly impaired cortisol response to ACTH stimulation, elevated renin and ACTH. Family history revealed that two maternal uncles had died soon after birth. A third uncle failed to thrive during infancy but improved with a course of cortisone, then being untreated until further investigation revealed adrenal insufficiency. A fourth uncle died aged 10 days, with urinary salt loss and hypoplastic adrenal glands at postmortem. Molecular studies on the proband, his mother, maternal grandmother, and surviving uncle showed a novel C to G substitution at nucleotide position 794 (missense mutation T265R) in the DAX1 (NR0B1) gene. The proband has responded well to steroid replacement but has proved sensitive to 9alpha-fludrocortisone treatment, developing hypertension on a dose of 133 microg/m(2)/day. At 8.8 years he was noted to have testicular volumes of 4 ml, despite no other evidence of secondary sexual development and prepubertal gonadotrophin levels. Novel features of this family include a novel DAX1 mutation, marked variability in age of presentation, hypertension on 'standard' doses of 9alpha-fludrocortisone and mild testicular enlargement.

Anthropometric foot structure of peripubescent children with excessive versus normal body mass: a cross-sectional study.

BACKGROUND: A variety of musculoskeletal problems have been associated with excessive body mass in children, including structural foot problems. METHODS: Two hundred children aged 9 to 12 years were recruited to evaluate the effect of body mass on foot structure. Three reliable anthropometric measures were recorded: foot length, forefoot width, and navicular height. RESULTS: Following independent sample t test analysis of the data, significant differences were found for the three anthropometric variables when children with normal body mass were compared with those with excessive body mass. The research indicates that foot length and width increase with body mass, whereas navicular height drops. CONCLUSIONS: Excessive body mass affects the discrete anthropometric structure of the peripubescent foot. With the growing concern about childhood obesity, further research is essential to develop a comprehensive understanding of the issues identified and to quantify the findings presented here.

Outcome of Doctors Attending the European Society for Paediatric Endocrinology Winter Schools 2008-2014.

BACKGROUND/AIMS: Since 1995, the European Society for Paediatric Endocrinology (ESPE) has hosted Winter School (WS), a 5-day interactive meeting of 25 trainees and 7 teachers designed to cover all main endocrine topics. The aim of the present study was to determine subsequent outcome in ex-WS "students." METHODS: A questionnaire was sent in August 2016 to all ESPE WS participants between 2008 and 2014. Information was requested on job/training status at WS attendance and in 2016, and subsequent involvement with ESPE. RESULTS: Of 174 participants (144 women, 30 men) including 5 attending two WS, 129 (74.5%) responded. At the time of WS/2016 survey 58/3 participants were junior trainees, 38/21 senior trainees, and 33/101 consultants. One hundred and seventeen (90.6%) responders were still involved with endocrinology, 107 (82%) rating WS as having a strong/very strong influence on their careers. Following WS, 80/174 (46%) participants had attended at least one ESPE main meeting, 28 (16%) had been awarded ESPE fellowships, and 34 (19%) had become ESPE members. CONCLUSIONS: The great majority of WS participants responding to the questionnaire are still involved with endocrinology and rated WS as influential. This favourable outcome supports the continuing funding of WS and similar educational programmes.

How well does the capillary thyroid-stimulating hormone test for newborn thyroid screening predict the venous free thyroxine level?

OBJECTIVES: To determine, in newborn infants referred with elevated capillary thyroid-stimulating hormone (TSH), a threshold below which a frankly subnormal venous free thyroxine (fT4) level of <10 pmol/L is unlikely, so that treatment with levo-thyroxine (L-T4) might be deferred until venous thyroid function tests (TFTs) become available. SUBJECTS AND METHODS: All infants referred in Scotland since 1979 with capillary TSH elevation were studied, with particular focus on infants screened using the AutoDELFIA assay between 2002 and 2013. RESULTS: Of the 321 infants referred with capillary TSH elevation using AutoDELFIA, 35 were excluded (fT4/TSH unavailable (12), venous sample either preceding or >10 days after capillary sampling (13, 10)), leaving 286 eligible for analysis (208 definite/probable hypothyroidism, 61 transient TSH elevation, 17 of uncertain thyroid status). Capillary TSH and venous T4 were strongly correlated (Spearman's rank correlation coefficient -0.707355). The optimal capillary TSH threshold for predicting a venous fT4 of <10 pmol/L was found to be >40 mU/L (90.3% sensitivity and 65.9% specificity compared with 90.25% and 59.1% for >35 mU/L and 88.3% and 68.2% for >45 mU/L). 93 infants (32.5%) had capillary TSH ≤40 mU/L at referral of whom 15 (9.7%) had venous fT4 <10 pmol/L, comprising seven with true congenital hypothyroidism, five with transient TSH elevation and three with uncertain status, two of whom died. CONCLUSION: For infants in whom capillary TSH is ≤40 mU/L, it is reasonable to defer L-T4 treatment until venous TFT results are known provided that the latter become available quickly.

Maternal age in patients with septo-optic dysplasia.

AIM: To determine whether patients with septooptic dysplasia (SOD) are of normal birth weight and gestation but are born to mothers who are significantly younger than average. METHODS: Retrospective study of 30 patients with SOD attending the Royal Hospital for Sick Children, Glasgow. Birth data for the Scottish population were used for comparison. RESULTS: Mean birth weight was 3.42 (range 2.66-4.18) kg. One patient was born preterm while the rest were born at term. Data for the Scottish population were available from 1979 onwards and 26 patients born after this year were selected for analysis. Median maternal age in this group was 21 (range 16-41) years, significantly lower than the median maternal age for Scotland of 27.12 (range 25.8-28.6) years (95% CI 4.8-8.0 years). CONCLUSION: Patients with SOD are of normal birth weight and gestation but are born to mothers who are significantly younger than average.

Early identification of pituitary dysfunction in congenital nasal pyriform aperture stenosis: recommendations based on experience in a single centre.

BACKGROUND: Congenital nasal pyriform aperture stenosis (CNPAS) is an increasingly recognised cause of upper airway obstruction associated with midline abnormalities. Studies have described pituitary dysfunction in 40% of patients. We aimed to develop guidelines for: (a) the early identification of pituitary insufficiency to minimise surgical risk and (b) to stratify patients for follow-up. METHODS: Retrospective case note review of patients with CNPAS between 2000 and 2014 in a tertiary paediatric unit. RESULTS: 20 patients (12 female:8 male) were analysed; 16 were diagnosed during the neonatal period while 4 were diagnosed later. There was no consistent approach in the evaluation of the pituitary axis at diagnosis. Pituitary dysfunction was identified in 3 (15%) patients, 2 of whom were found during evaluation of short stature in mid-late childhood. Hypoglycaemia and conjugated hyperbilirubinaemia, but not the degree of stenosis, were highly predictive of pituitary dysfunction (p < 0.05). Available height standard deviation score (SDS) data at 1 year of 70% of our patients identified both of the late-diagnosed growth hormone-deficient patients, with SDS of -2.6 and -3.6, respectively. CONCLUSION: All CNPAS patients should have MRI of the brain and baseline endocrine investigations at diagnosis. Growth monitoring for at least 1 year is recommended as low, or falling, height SDS at 1 year is a good predictor of pituitary dysfunction.

Effect of oxandrolone and timing of oral ethinylestradiol initiation on pubertal progression, height velocity and bone maturation in the UK Turner study.

BACKGROUND: A UK study showed final height in Turner syndrome (TS) girls receiving growth hormone is affected by age at pubertal induction and oxandrolone (Ox). Using data from that study, we analysed the effect of timing of oral ethinylestradiol (EE2) and Ox on height velocity (HV), bone maturation and pubertal progression, and compared growth response in EE2-treated versus spontaneous puberty. METHODS: Analysis of HV, bone age and pubertal stage in 92 TS girls (7-13 years) randomised to Ox (0.05 mg/kg/day; max: 2.5 mg/day) or placebo from 9 years, and EE2 (year 1: 2 µg/day; year 2: 4 µg/day; year 3: 6/8/10 µg/day×4 months) or placebo at 12 years with EE2 at 14 years. Girls enrolled at >12.25 years received EE2 at 14 years ('late group'). RESULTS: Fifty-six girls were randomised to EE2 at 12 years (n=28, 11 Ox) or 14 years (n=28, 13 Ox); there were 19 girls in the late group (9 Ox) and 17 girls with spontaneous puberty (10 Ox). Girls receiving EE2 at 12 versus 14 years had faster bone maturation, but neither group showed acceleration. Ox increased HV without altering bone maturation or pubertal progression. Girls with spontaneous puberty had greater pubertal growth (mean PHV 8.5 cm/year; p<0.001) and height gain (p<0.001) than EE2-treated girls despite similar mean enrolment height SD and dysmorphology scores. CONCLUSION: Pubertal induction with EE2 does not replicate the acceleration observed in unaffected girls or TS girls with spontaneous puberty.

Functional characterisation of the H365Y mutation of the 21-hydroxylase gene in congenital adrenal hyperplasia.

The study subject was a 13 day-old boy admitted to hospital, with weight loss since birth. He presented with the vomiting and hypotension that are classical features of congenital adrenal hyperplasia (CAH). The most common type of CAH is an autosomal recessive disorder caused by mutations in the 21-hydroxylase (CYP21A2) gene. To examine the CYP21A2 gene, gene-specific PCR was carried out, followed by sequencing. The baby was shown to be a compound heterozygote H365Y/R356W for two CYP21A2 gene mutations each inherited from a different parent. One of the mutations has not previously been functionally characterised. The mutations were reconstructed in an expression plasmid and characterised in vitro after transient transfection into human embryonic kidney (HEK293T) and hepatoblastoma (C3A) cell lines followed by measurement of enzyme activity. The CYP21A2 H365Y mutant exhibited minimal 21-hydroxylase activity to convert 17-hydroxyprogesterone to 11-deoxycortisol or progesterone to 11-deoxycorticosterone. Western immunoblotting indicated that the H365Y enzyme was produced in more variable amounts than wild type; in particular, the H365Y mutant protein may be unstable and/or subject to a more rapid degradation by the human proteosome as well as catalytically inefficient. The double mutant genotype with a severe mutation on each allele is compatible with the clinical presentation.