Aetiological bases of 46,XY disorders of sex development in the Hong Kong Chinese population.

OBJECTIVE: Disorders of sex development are due to congenital defects in chromosomal, gonadal, or anatomical sex development. The objective of this study was to determine the aetiology of this group of disorders in the Hong Kong Chinese population. SETTING: Five public hospitals in Hong Kong. PATIENTS: Patients with 46,XY disorders of sex development under the care of paediatric endocrinologists between July 2009 and June 2011. MAIN OUTCOME MEASURES: Measurement of serum gonadotropins, adrenal and testicular hormones, and urinary steroid profiling. Mutational analysis of genes involved in sexual differentiation by direct DNA sequencing and multiplex ligation-dependent probe amplification. RESULTS: Overall, 64 patients were recruited for the study. Their age at presentation ranged from birth to 17 years. The majority presented with ambiguous external genitalia including micropenis and severe hypospadias. A few presented with delayed puberty and primary amenorrhea. Baseline and post-human chorionic gonadotropin-stimulated testosterone and dihydrotestosterone levels were not discriminatory in patients with or without AR gene mutations. Of the patients, 22 had a confirmed genetic disease, with 11 having 5α-reductase 2 deficiency, seven with androgen insensitivity syndrome, one each with cholesterol side-chain cleavage enzyme deficiency, Frasier syndrome, NR5A1-related sex reversal, and persistent Müllerian duct syndrome. CONCLUSIONS: Our findings suggest that 5α-reductase 2 deficiency and androgen insensitivity syndrome are possibly the two most common causes of 46,XY disorders of sex development in the Hong Kong Chinese population. Since hormonal findings can be unreliable, mutational analysis of the SRD5A2 and AR genes should be considered the first-line tests for these patients.

Vascular calcification in a young patient with end-stage renal disease.

Vascular calcification in children with long-standing dialysis is a unique phenomenon. Hyperphosphataemia and hyperparathyroidism are the major pathogenic risk factors. We describe a young patient with end-stage renal disease diagnosed since childhood and underwent prolonged dialysis therapy. He was admitted for recurrent episodes of acute joint pain. Investigations confirmed diffuse periarticular, vascular, and intracardiac calcifications which were rarely seen in the young population. He underwent parathyroidectomy and incidentally found to have a co-existing papillary carcinoma of thyroid. After parathyroidectomy, serial X-rays showed resorption of these calcifications.

Delayed diagnosis of adrenal insufficiency in a patient with severe penoscrotal hypospadias due to two novel P450 side-change cleavage enzyme (CYP11A1) mutations (p.R360W; p.R405X).

CONTEXT: Cytochrome P450 side-chain cleavage enzyme (CYP11A1) catalyses the first and rate-limiting step of steroidogenesis, the conversion of cholesterol to pregnenolone. CYP11A1 deficiency is commonly associated with adrenal insufficiency, and in 46,XY individuals, with variable degrees of disorder of sex development (DSD). PATIENT AND METHODS: The patient was born with hyperpigmentation, micropenis, penoscrotal hypospadias, and mild cryptorchidism. Biochemical and hormonal findings were normal except for low testosterone and low-borderline cortisol. However, no short synacthen test was undertaken. Development was unremarkable apart from an episode labeled as sepsis with documented hyperkalemia and elevated C-reactive protein at age 15 days. Diagnosis of 46,XY DSD was made at age 2.5 months. Progression of hyperpigmentation prompted further investigations and the diagnosis of adrenal insufficiency was established at 2 years with raised ACTH, normal renin activity, and failure of cortisol to respond to short synacthen test. Genetic analyses were performed. The novel CYP11A1 mutations were characterized in vitro and in silico. RESULTS: The patient was compound heterozygous for two novel CYP11A1 mutations, p.R360W and p.R405X. p.R360W retained 30-40% of wild-type activity. In silico analyses confirmed these findings and indicated that p.R405X is severe. CONCLUSIONS: This study demonstrates the pathogenicity of two novel CYP11A1 mutations found in a patient with delayed diagnosis of CYP11A1 deficiency. Patients with partial deficiencies of steroidogenic enzymes are at risk to be misdiagnosed if adrenal function is not assessed. The adrenocortical function should be routinely assessed in all patients with DSD including severe hypospadias of unknown origin to prevent life-threatening adrenal crises.

Enzyme replacement therapy for mucopolysaccharidosis VI (Maroteaux-Lamy syndrome): experience in Hong Kong.

Mucopolysaccharidosis VI (Maroteaux-Lamy syndrome) is a very rare inherited lysosomal storage disease. We evaluated the efficacy and safety of weekly infusions of recombinant human arylsulfatase B as enzyme replacement therapy for two patients in whom this condition was advanced. The primary outcome variables were the distance walked in a 6-minute walk test, forced vital capacity, and ejection fraction. The secondary outcome variables were the number of stairs climbed in a 3-minute stair climbing test, joint mobility, urinary glycosaminoglycan excretion, auto-continuous positive airway pressure study and liver size. After 24 weeks of treatment, patient A walked 40 m (36%) and patient B walked 66 m (58%) more in the walk test than at baseline. After 48 weeks, in patient A the corresponding improvements were 142 m (129%) in the walk test and 33 stairs (60%) in the 3-minute stair climbing test, and in patient B the respective improvements were 198 m (174%) and 77 stairs (140%). There was a significant decline in urinary glycosaminoglycan excretion and improvement in range of motion of joints in both patients. The auto-continuous positive airway pressure study revealed improvements in patient A, while other efficacy variables remained static. There were no drug-related adverse events or allergic reactions reported during and after the infusions of recombinant human arylsulfatase B. Recombinant human arylsulfatase B significantly improves endurance and reduces urinary glycosaminoglycan excretion. The drug is generally safe and well tolerated.

Molecular analysis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency in Hong Kong Chinese patients.

BACKGROUND: Congenital adrenal hyperplasia (CAH) caused by 21-hydroxylase deficiency (21OHD) is an autosomal recessive disorder due to mutation in the CYP21A2 gene. OBJECTIVE: To elucidate the genetic basis of 21-hydroxylase-deficient CAH in Hong Kong Chinese patients. PATIENTS AND METHODS: Mutational analysis of the CYP21A2 gene was performed on 35 Hong Kong Chinese patients with 21OHD using direct DNA sequencing and multiplex ligation-dependent probe amplification (MLPA). RESULTS: The genetic findings of 21 male and 14 female patients are the following: c.293-13A/C>G (intron 2 splice site; 20 alleles), p.I172N (13), p.R356W (7), p.Q318X (4). A total of 20 mutant alleles contained gross deletion/conversion of all or part of the CYP21A2 gene. A novel mutation, c.1367delA (p.D456fs), was detected in one patient. One patient had only a heterozygous mutation detected. Out of 35 patients, 16 would have been incorrectly genotyped if either DNA sequencing or MLPA alone was used for molecular analysis. CONCLUSIONS: The frequency of various mutations in the studied patients differs from those reported in other Asian populations. Gross deletion/conversion accounts for nearly one-third of the genetic defects. Therefore, laboratories must include methods for detecting point mutations as well as gross deletions/conversions to avoid misinterpretation of genotype. Genotyping has increasingly been proven to be a useful tool for supplementing, if not replacing, hormonal profiling for the diagnosis of 21OHD.

Ambiguous genitalia, impaired steroidogenesis, and Antley-Bixler syndrome in a patient with P450 oxidoreductase deficiency.

Cytochrome P450 oxidoreductase deficiency is a recently established autosomal recessive disease characterised by ambiguous genitalia, impaired steroidogenesis, and skeletal malformations, referred to as Antley-Bixler syndrome. Clinical manifestations in affected patients are highly variable. We report on a girl with P450 oxidoreductase deficiency who presented with virilisation at birth. There was transient maternal virilisation during pregnancy as well. She was initially diagnosed with congenital adrenal hyperplasia caused by 21-hydroxylase deficiency and/or aromatase deficiency. At 1 year of age, skeletal abnormalities suggestive of Antley-Bixler syndrome were detected. Molecular analysis of the fibroblast growth factor receptor 2 (FGFR2) gene was normal but POR gene analysis showed that she was homozygous for an R457H missense mutation. The diagnosis, P450 oxidoreductase deficiency, was confirmed. Results of her endocrine studies and urinary steroid profiling are also presented.

Enzyme replacement therapy for infantile Pompe disease during the critical period and identification of a novel mutation.

Pompe disease (acid maltase deficiency, glycogen storage disease type II) is a rare progressive autosomal recessive disorder caused by a deficiency of lysosomal hydrolase acid alpha-glucosidase. Historically, infantile-onset Pompe disease presents with cardiomegaly, hepatomegaly, weakness and hypotonia leading to death caused by cardiorespiratory failure in the first year of life. Enzyme replacement therapy has recently become available and has been shown to be effective in prolonging survival and improving respiratory performance. In this article, we report a case of infantile-onset Pompe disease successfully managed with enzyme replacement therapy during the critical period. We would like to highlight the occurrence of sudden cardiac arrest in our patient during the early course of enzyme replacement therapy, which has not been reported before. A novel mutation was also identified in the family.

Frasier syndrome: a rare cause of delayed puberty.

We report on a post-renal transplant patient who presented with delayed pubertal development at the age of 15 years. She had a normal female phenotype. Blood analysis showed hypergonadotropic hypogonadism. Her karyotype was 46,XY. DNA analysis showed a heterozygous mutation in the WT1 gene (C to T mutation at position +4 of the splice donor site within intron 9). A diagnosis of Frasier syndrome was made and she underwent laparoscopic gonadectomy. This case illustrates that, while delayed puberty is common in children with chronic illness, clinicians should be particularly aware of the possibility of Frasier syndrome in those with progressive glomerulopathy and delayed puberty. DNA analysis is a useful means of confirming the diagnosis.

Ammonia detoxification by continuous venovenous haemofiltration in an infant with urea cycle defect.

We report the case of a newborn baby with carbamoyl phosphate synthetase deficiency. He presented at 2 weeks of life, deteriorating to a state of hyperammonaemic coma and respiratory failure. Rapid detoxification was successfully achieved by continuous venovenous haemofiltration while a definitive diagnosis and treatment were determined. The ammonia clearance achieved by continuous venovenous haemofiltration was greater than 20 mL/min/m(2), which is superior to that achieved by peritoneal dialysis and arteriovenous haemofiltration in this age-group.

Glucose-6-phosphatase gene (727G-->T) splicing mutation is prevalent in Hong Kong Chinese patients with glycogen storage disease type 1a.

Glycogen storage disease type la (GSD1a) is an autosomal recessive metabolic disorder caused by a deficiency in glucose-6-phosphatase (G6Pase). We analyzed the G6Pase genes of two unrelated Chinese families with GSD1a. DNA sequencing of all five exons and the exon-intron boundaries revealed a G T transversion at nucleotide 727 (727G-->T) in exon 5, which has previously been reported to cause abnormal splicing. In one family, the subject and her affected sister were confirmed to be homozygous for this mutation and their parents to be heterozygotes. In the other family, the proband was identified to be heterozygous for this mutation, and a novel mutation, the 341delG in exon 2, was identified. This mutation alters the reading frame and creates a stop codon TAA 15 codons downstream from the mutation, resulting in a truncated protein. Family studies revealed that the father was heterozygous for the 727G-->T mutation and that the mother was heterozygous for the 341delG mutation. This is the first time that the 727G T mutation has been found in Chinese patients or outside Japan. Since we only tested two GSD1a families and found 727G-->T in both, we believe that this mutation may also be prevalent in our local Chinese population. To investigate allele frequencies, we screened 385 Chinese healthy volunteers and found two asymptomatic carriers. Our findings suggest that the 727G-->T mutation is indeed prevalent in Hong Kong.