Monitoring Skull Base Abnormalities in Children with Osteogenesis Imperfecta - Review of Current Practice and a Suggested Clinical Pathway.

OBJECTIVES: In the context of a lack of national consensus on the benefits of skull base imaging in children with osteogenesis imperfecta (OI), this study aims to analyse and correlate the clinical symptoms and radiological images of children with severe OI. METHODS: A retrospective case notes and image analysis was carried out on children with complex OI between 2012 and 2018 at a specialist tertiary centre. Data were collected on patient demographic factors, clinical data, imaging findings (presence of Wormian bones, platybasia, basilar impression (McGregor's technique) and basilar invagination (McRae's technique)), and clinical features at the time of imaging. RESULTS: Of the 127 patients in the OI database, 94 were included. A total of 321 radiographs, 21 CT scans and 39 MRI scans were analysed. Average frequency of radiographs was 8 per 10 years. Of the 94 patients, 58 (62%), 10 (11%), 1 (1%) demonstrated platybasia, basilar impression, and basilar invagination, respectively. Of the radiographs analysed, platybasia, basilar impression, basilar invagination, and the presence of Wormian bones, could not be evaluated in 71 (22.3%), 48 (15.2%), 61 (19.5%) and 28 (9.4%) radiographs respectively (due to poor positioning, anatomical abnormalities, and poor image quality). Of the 140 radiographs with platybasia, 17 (12%) also demonstrated basilar impression compared to only 3 (2.9%) out of the 99 without platybasia (p = 0.03). No significant associations were seen between the presence of Wormian bones and basilar impression. Of the 39 MRIs, additional information on CSF flow rate, spinal cord signal and cerebellar morphology was reported in 14 (36%). There was a lack of concordance between MRI and matched radiographs in 7.1% (1/14) and 36% (5/14) for platybasia and basilar impression respectively, with full concordance for basilar invagination. Fewer than 5% had positive clinical symptoms/signs at the time of imaging; 2% (7/321) had macrocephaly, 0.6% (2/321) headache, all other neurological features were absent). Clinical features were not documented in >85% of patients. CONCLUSION: The apparent low prevalence of clinical symptoms and signs and of radiologically identified cranio-cervical abnormalities, suggests that current levels of serial imaging may be excessive. Until larger prospective studies clarify these issues, we suggest a clinical pathway for base of skull imaging which proposes a risk stratification approach to radiographic frequency and suggests parameters for proceeding to MRI.

Clinical spectrum, treatment and outcome of children with suspected diagnosis of chronic inflammatory demyelinating polyradiculoneuropathy.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a treatable chronic disorder of the peripheral nervous system. We retrospectively studied 30 children with a suspected diagnosis of CIDP. The diagnosis of CIDP was compared against the childhood CIDP revised diagnostic criteria 2000. Of the 30 children, five did not meet the criteria and four others met the criteria but subsequently had alternative diagnosis, leaving a total of 21 children (12 male) with CIDP as the final diagnosis. Thirteen children presented with chronic symptom-onset (>8 weeks). The majority presented with gait difficulties or pain in legs (n = 16). 12 children (57%) met the neurophysiological criteria and 18/19 (94%) met the cerebrospinal fluid criteria. Nerve biopsy was suggestive in 3/9 (33%), with magnetic resonance imaging supportive in 9/20 (45%). Twenty-one children received immuno-modulatory treatment at first presentation, of which majority (n = 19, 90%) received IVIG (immunoglobulin) monotherapy with 13 (68%) showing a good response. 8 children received second line treatment with either IVIG or steroids or plasmapharesis (PE) and 4 needed other immune-modulatory agents. During a median follow-up of 3.6 years, 9 (43%) had a monophasic course and 12 (57%) had a relapsing-remitting course. At last paediatric follow up 7 (33%) were off all treatment, 9 (43%) left with no or minimal residual disability and 6 (28%) children were walking with assistance (n = 3) or were non-ambulant (n = 3). Our review highlights challenges in the diagnosis and management of paediatric CIDP. It also confirms that certain metabolic disorders may mimic CIDP.

Compound heterozygous variants in NBAS as a cause of atypical osteogenesis imperfecta.

BACKGROUND: Osteogenesis imperfecta (OI), the commonest inherited bone fragility disorder, affects 1 in 15,000 live births resulting in frequent fractures and reduced mobility, with significant impact on quality of life. Early diagnosis is important, as therapeutic advances can lead to improved clinical outcome and patient benefit. REPORT: Whole exome sequencing in patients with OI identified, in two patients with a multi-system phenotype, compound heterozygous variants in NBAS (neuroblastoma amplified sequence). Patient 1: NBAS c.5741G>A p.(Arg1914His); c.3010C>T p.(Arg1004*) in a 10-year old boy with significant short stature, bone fragility requiring treatment with bisphosphonates, developmental delay and immunodeficiency. Patient 2: NBAS c.5741G>A p.(Arg1914His); c.2032C>T p.(Gln678*) in a 5-year old boy with similar presenting features, bone fragility, mild developmental delay, abnormal liver function tests and immunodeficiency. DISCUSSION: Homozygous missense NBAS variants cause SOPH syndrome (short stature; optic atrophy; Pelger-Huet anomaly), the same missense variant was found in our patients on one allele and a nonsense variant in the other allele. Recent literature suggests a multi-system phenotype. In this study, patient fibroblasts have shown reduced collagen expression, compared to control cells and RNAseq studies, in bone cells show that NBAS is expressed in osteoblasts and osteocytes of rodents and primates. These findings provide proof-of-concept that NBAS mutations have mechanistic effects in bone, and that NBAS variants are a novel cause of bone fragility, which is distinguishable from 'Classical' OI. CONCLUSIONS: Here we report on variants in NBAS, as a cause of bone fragility in humans, and expand the phenotypic spectrum associated with NBAS. We explore the mechanism underlying NBAS and the striking skeletal phenotype in our patients.

Recessive axonal Charcot-Marie-Tooth disease due to compound heterozygous mitofusin 2 mutations.

OBJECTIVE: Mutations in mitofusin 2 (MFN2) are the most common cause of axonal Charcot-Marie-Tooth disease (CMT2). Over 50 mutations have been reported, mainly causing autosomal dominant disease, though families with homozygous or compound heterozygous mutations have been described. We present 3 families with early-onset CMT2 associated with compound heterozygous MFN2 mutations. Transcriptional analysis was performed to investigate the effects of the mutations. METHODS: Patients were examined clinically and electrophysiologically; parents were also examined where available. Genetic investigations included MFN2 DNA sequencing and dosage analysis by multiplex ligation-dependent probe amplification. MFN2 mRNA transcripts from blood lymphocytes were analyzed in 2 families. RESULTS: Compound heterozygosity for MFN2 mutations was associated with early-onset CMT2 of varying severity between pedigrees. Parents, where examined, were unaffected and were heterozygous for the expected mutations. Four novel mutations were detected (one missense, one nonsense, an intragenic deletion of exons 7 + 8, and a 3-base pair deletion), as well as 2 previously reported missense mutations. Transcriptional analysis demonstrated aberrant splicing of the exonic deletion and indicated nonsense-mediated decay of mutant alleles with premature truncating mutations. CONCLUSIONS: Our findings confirm that MFN2 mutations can cause early-onset CMT2 with apparent recessive inheritance. Novel genetic findings include an intragenic MFN2 deletion and nonsense-mediated decay. Carrier parents were asymptomatic, suggesting that MFN2 null alleles can be nonpathogenic unless coinherited with another mutation.

A severity scoring tool to assess the neurological features of neuronopathic Gaucher disease.

Type III Gaucher disease is one of the three recognized subtypes of Gaucher disease, an inherited deficiency of lysosomal glucocerebrosidase. Phenotypically there is a wide spectrum of visceral and neurological manifestations. Enzyme replacement is effective in managing the visceral disease; however, the neurological manifestations remain a more challenging obstacle. There is an unfulfilled need to reliably monitor neurological disease and its response to treatment. A severity scoring tool was developed through neurological domain identification, item generation and tool formation. Domain identification was established based on a retrospective single centre study (n = 15) and a systematic review of publications. Forty-seven patients with neuronopathic Gaucher disease were then assessed using the tool to establish the clinical and statistical reliability of each domain. Judgement quantification of the tool was established through a process of content validity involving five European experts. Content validity is considered to be most effective when undertaken systematically. Concurrent validity and feasibility of the tool was also highlighted. This process allowed a revised and validated version of the tool to be developed.

Congenital muscular dystrophy with secondary merosin deficiency and normal brain MRI: a novel entity?

We describe two Scottish siblings affected by a form of congenital muscular dystrophy characterised by a severe clinical phenotype, similar to that observed in the 6q-linked merosin-deficient CMD but in whom brain MRI and cognitive development were normal. The maximal function achieved in the 2 siblings was sitting independently. Serum CK were grossly elevated and the skin and muscle biopsies showed a severe reduction of merosin in both. The normal brain MRI and normal cognitive development distinguish this form from Fukuyama congenital muscular dystrophy, muscle-eye-brain disease or other forms of CMD with secondary partial merosin deficiency and abnormal brain MRI and/or mental retardation. Linkage analysis excluded all the known loci for CMD. We propose that this may represent a novel variant of CMD.

Hydrocortisone replacement therapy in children and adolescents with hypopituitarism.

OBJECTIVE: Appropriate replacement doses of glucocorticoid are important to determine in primary and secondary adrenal deficiency in children, both to avoid the risks of hypoglycaemia and adrenal crisis associated with undertreatment, and to avoid growth suppression and reduced final height potential associated with steroid excess. The aim of this study was to assess how closely conventional twice daily hydrocortisone administration mimics physiological cortisol secretion in a group of ACTH-deficient children and adolescents. PATIENTS: Fifty children and adolescents (aged 3-20 years) were studied who had had surgery +/- radiotherapy to the hypothalamopituitary region for removal of a craniopharyngioma. The patients were subdivided into two groups: group I comprised 44 patients known to be ACTH deficient (as determined by glucagon or insulin provocation tests of anterior pituitary function performed after surgery) and maintained on twice daily oral hydrocortisone replacement; group II comprised six patients known to be ACTH sufficient at their last assessment of pituitary function and not on hydrocortisone replacement. A third group of 10 boys (aged 7-13 years) who had no known endocrinopathy were used as controls (group III). MEASUREMENTS: After intravenous cannula insertion, blood samples were taken every 2h for measurement of plasma cortisol and glucose over a period of 24h. Patients in group I continued on their usual doses of hydrocortisone, prescribed at 0800 and 1800 h. RESULTS: The mean total daily replacement dose of hydrocortisone for patients in group I was 12.3 mg/m2/ day (range, 5.5-18.5). On the conventional twice daily dose regimen, there was a supraphysiological medium plasma cortisol level (629 nmol/l, range 185-1600; z = -3.76, P = 0.0002) 2 h after the morning dose relative to the control group, and a prolonged and unphysiological nadir from 1400-1800 h (median at 1600 h 42 nmol/l, range 13-1170; z = -3.13, P < 0.002) before the second dose of hydrocortisone was administered. Cortisol values were low, and often negligible, during the early hours of the morning (median at 0600 h 15 nmol/l, range 13-277, z = -4.87, P < 0.00001) and spontaneous hypoglycaemia was documented in one patient on a single 0800 h sample. One patient in group II was shown to be unequivocally cortisol deficient and median cortisol values for the remaining five suggested a suboptimal rise in plasma cortisol during the early hours of the morning. CONCLUSION: Our cohort of patients provides an excellent model for the study of glucocorticoid replacement in cortisol-deficient children and adolescents and shows, as in adults, that the aim of mimicking the physiological nyctohemeral secretion of cortisol is difficult to achieve in practice and raises a number of important considerations unique to steroid substitution therapy in this age group.

Growth and endocrine sequelae of craniopharyngioma.

The growth and endocrine sequelae of 75 children (33 girls and 42 boys) with craniopharyngioma, treated from 1973 to 1994, were studied by retrospective review and by follow up assessment in 66 survivors, with a mean time from initial surgery of 6.7 years (range 1.5 to 19.8 years). Although infrequently complained of, 71% of patients had symptoms to suggest an endocrinopathy at diagnosis. After surgery, multiple endocrinopathies were almost universal, such that 75% of children had panhypopituitarism at follow up. Hypoadrenal crises in association with intercurrent illness contributed significantly to morbidity and mortality, as did the metabolic consequences of concomitant antidiuretic hormone (ADH) insufficiency and absent thirst. Final height in 25 patients was significantly below genetic target height, particularly in the girls, with loss of height potential occurring during the pubertal years. The endocrine morbidity associated with craniopharyngioma and its treatment remains high but manageable with appropriate hormone replacement. However, the combination of ADH insufficiency and an impaired sense of thirst following aggressive surgery and severe hypothalamic injury remains one of the most complex management problems.

Growth arrest despite growth hormone replacement, post-craniopharyngioma surgery.

Children with growth failure, whether secondary to an endocrinopathy such as growth hormone deficiency or secondary to neurological handicap with poor nutrient intake, grow at a subnormal rate but it is most unusual for a child to have complete growth arrest.