Nithiwat Vatanavicharn

Phenotypic features of carbohydrate sulfotransferase 3 (CHST3) deficiency in 24 patients: Congenital dislocations and vertebral changes as principal diagnostic features†

We recently reported on the deficiency of carbohydrate sulfotransferase 3 (CHST3; chondroitin‐6‐sulfotransferase) in six subjects diagnosed with recessive Larsen syndrome or humero‐spinal dysostosis [Hermanns et al. (2008); Am J Hum Genet 82:1368–1374]. Since then, we have identified 17 additional families with CHST3 mutations and we report here on a series of 24 patients in 23 families. The diagnostic hypothesis prior to molecular analysis had been: Larsen syndrome (15 families), humero‐spinal dysostosis (four cases), chondrodysplasia with multiple dislocations (CDMD “Megarbane type”; two cases), Desbuquois syndrome (one case), and spondylo‐epiphyseal dysplasia (one case). In spite of the different diagnostic labels, the clinical features in these patients were similar and included dislocation of the knees and/or hips at birth, clubfoot, elbow joint dysplasia with subluxation and limited extension, short stature, and progressive kyphosis developing in late childhood. The most useful radiographic clues were the changes of the lumbar vertebrae. Twenty‐four different CHST3 mutations were identified; 16 patients had homozygous mutations. We conclude that CHST3 deficiency presents at birth with congenital dislocations of knees, hips, and elbows, and is often diagnosed initially as Larsen syndrome, humero‐spinal dysostosis, or chondrodysplasia with dislocations. The incidence of CHST3 deficiency seems to be higher than assumed so far. The clinical and radiographic pattern (joint dislocations, vertebral changes, normal carpal age, lack of facial flattening, and recessive inheritance) is characteristic and distinguishes CHST3 deficiency from other disorders with congenital dislocations such as filamin B‐associated dominant Larsen syndrome and Desbuquois syndrome.

BMPER Mutation in Diaphanospondylodysostosis Identified by Ancestral Autozygosity Mapping and Targeted High-Throughput Sequencing

Diaphanospondylodysostosis (DSD) is a rare, recessively inherited, perinatal lethal skeletal disorder. The low frequency and perinatal lethality of DSD makes assembling a large set of families for traditional linkage-based genetic approaches challenging. By searching for evidence of unknown ancestral consanguinity, we identified two autozygous intervals, comprising 34 Mbps, unique to a single case of DSD. Empirically testing for ancestral consanguinity was effective in localizing the causative variant, thereby reducing the genomic space within which the mutation resides. High-throughput sequence analysis of exons captured from these intervals demonstrated that the affected individual was homozygous for a null mutation in BMPER, which encodes the bone morphogenetic protein-binding endothelial cell precursor-derived regulator. Mutations in BMPER were subsequently found in three additional DSD cases, confirming that defects in BMPER produce DSD. Phenotypic similarities between DSD and Bmper null mice indicate that BMPER-mediated signaling plays an essential role in vertebral segmentation early in human development.

Clinical and molecular findings in Thai patients with isolated methylmalonic acidemia

Isolated methylmalonic acidemia (MMA) is a genetically heterogeneous organic acid disorder caused by either deficiency of the enzyme methylmalonyl-CoA mutase (MCM), or a defect in the biosynthesis of its cofactor, adenosyl-cobalamin (AdoCbl). Herein, we report and review the genotypes and phenotypes of 14 Thai patients with isolated MMA. Between 1997 and 2011, we identified 6 mut patients, 2 cblA patients, and 6 cblB patients. The mut and cblB patients had relatively severe phenotypes compared to relatively mild phenotypes of the cblA patients. The MUT and MMAB genotypes were also correlated to the severity of the phenotypes. Three mutations in the MUT gene: c.788G>T (p.G263V), c.809_812dupGGGC (p.D272Gfs*2), and c.1426C>T (p.Q476*); one mutation in the MMAA gene: c.292A>G (p.R98G); and three mutations in the MMAB gene: c.682delG (p.A228Pfs*2), c.435delC (p.F145Lfs*69), and c.585-1G>A, have not been previously reported. RT-PCR analysis of a common intron 6 polymorphism (c.520-159C>T) of the MMAB gene revealed that it correlates to deep intronic exonization leading to premature termination of the open reading frame. This could decrease the ATP:cobalamin adenosyltransferase (ATR) activity resulting in abnormal phenotypes if found in a compound heterozygous state with a null mutation. We confirm the genotype-phenotype correlation of isolated MMA in the study population, and identified a new molecular basis of the cblB disorder.

Reversible leukoencephalopathy with acute neurological deterioration and permanent residua in classical homocystinuria: A case report

SummaryWe report a 24-year-old patient with underlying classical homocystinuria who developed acute neurological deterioration apparently induced by malnutrition secondary to poor compliance with treatment and pancreatitis. Neurological examination revealed stupor, tremor of the upper extremities, spasticity, and Babinski responses of the bilateral lower extremities. The biochemical profile, including marked hypermethioninaemia, hyperhomocysteinaemia, and decreased cystine in plasma, is consistent with cystathionine β-synthase deficiency. Brain MRI showed reversible diffuse white-matter changes without evidence of thrombosis. The clinical features and neuroimaging including diffusion-weighted MRI suggest a demyelinating process similar to other inborn errors of the transsulfuration pathway such as methylenetetrahydrofolate reductase deficiency, disorders affecting methylcobalamin metabolism (cobalamin C, D, E, and G disorders), and methionine adenosyltransferase deficiency. She was left with residual spastic paraparesis despite normal follow-up MRI. Our observation suggests that reversible demyelination is another neurological manifestation of classical homocystinuria; however, the pathophysiology is unknown.

Organic acid disorders detected by urine organic acid analysis: Twelve cases in Thailand over three-year experience

BACKGROUND Disorders of organic acid (OA) metabolism are generally detected by qualitative analysis of urine organic acids by gas chromatography/mass spectrometry (GC/MS) which was well established in developed countries since 1980s. Confirmation of the diagnosis of organic acid disorders by OA analysis, enzyme analysis and molecular study is a difficult task in developing countries. METHODS During 2001-2004, we had analysed 442 urine samples in 365 patients and identified 12 cases of organic acid disorders. RESULTS We identified the following disorders: alkaptonuria (ALK)=1, isovaleric acidemia (IVA)=3, propionic acidemia (PA)=2, methylmalonic acidemia (MMA)=3, glutaric aciduria, type I (GA-I)=1, multiple carboxylase deficiency (MCD)=1, and glutaric acidemia, type II (GA-II)=1. CONCLUSIONS OA disorders had never been diagnosed in Thailand before, until GC/MS technology was introduced to Thailand in 2001. Urine OA analysis also provided a diagnostic clue to other inborn errors of metabolism including amino acid disorders, urea cycle disorders, disorders of carbohydrate metabolism, and mitochondrial fatty acid oxidation disorders. Since then, we were able to diagnose numerous disorders, which led to prompt treatment and better outcome in our patients.

Multilayered patella: Similar radiographic findings in pseudoachondroplasia and recessive multiple epiphyseal dysplasia†

A multilayered patella is a characteristic radiographic finding of recessive multiple epiphyseal dysplasia (rMED) caused by DTDST mutations. However it has been recently reported in a dominant MED case with a COL9A2 mutation. We report on a new radiographic patellar finding in a patient with pseudoachondroplasia and a heterozygous COMP mutation. It is similar to the radiographic appearance of fusing multilayered patellae in rMED cases. This led us to search the International Skeletal Dysplasia Registry for similar abnormalities. We did not observe this finding in other skeletal dysplasias or other pseudoachondroplasia cases. However we found an accessory ossification center of the patella in another pseudoachondroplasia case. Thus, we hypothesize that variable defects of cartilage extracellular matrix can result in similar abnormal patellar ossifications, and emphasize the importance of a lateral knee radiograph in patients with the pseudoachondroplasia‐MED bone dysplasia group of disorders.

Diaphanospondylodysostosis: Six new cases and exclusion of the candidate genes, PAX1 and MEOX1†

We report on six cases from four families with the newly described skeletal disorder diaphanospondylodysostosis (DSD). The characteristic radiographic findings included abnormal ossification of vertebral bodies, posterior rib gaps, missing ribs, and a downward tilt of the pubic rami, but normal long bones. The typical facial features of DSD cases were ocular hypertelorism, a short nose, depressed nasal bridge, and low set ears. Other distinctive findings included a short neck with bell‐shaped thorax, and nephroblastomatosis. A history of consanguinity and affected siblings with unaffected parents supports autosomal recessive inheritance. Skeletal histology showed incomplete ossification of the ribs, vertebral bodies, and sacrum as well as incomplete formation of intervertebral discs. The posterior ribs were comprised of bone with intervening cartilage interrupted by dense fibrous tissue and skeletal muscle fascicles. These findings suggest abnormal development and differentiation of the paraxial mesoderm. Because of phenotypic similarities of DSD to Pax1 and Meox1 deficient mice, we sequenced genomic DNA from three unrelated DSD cases. No mutations were identified in the PAX1 and MEOX1 exons or flanking intronic sequences, excluding them as likely causative genes.

Phenotypic and mutation spectrums of Thai patients with isovaleric acidemia

Background:  Isovaleric acidemia (IVA) is an autosomal recessive disorder caused by deficiency of isovaleryl‐CoA dehydrogenase (IVD). Clinical features include vomiting, lethargy, metabolic acidosis, and “sweaty feet” odor. The pathognomonic metabolite, isovalerylglycine, is detected on urine organic acid analysis. Clinical diagnosis of IVA can be confirmed on mutation analysis of the IVD gene.

Carnitine–acylcarnitine translocase deficiency: Two neonatal cases with common splicing mutation and in vitro bezafibrate response

BACKGROUND Mitochondrial fatty acid oxidation (FAO) disorders are among the causes of acute encephalopathy- or myopathy-like illness. Carnitine-acylcarnitine translocase (CACT) deficiency is a rare FAO disorder, which represent an energy production insufficiency during prolonged fasting, febrile illness, or increased muscular activity. CACT deficiency is caused by mutations of the SLC25A20 gene. Most patients developed severe metabolic decompensation in the neonatal period and died in infancy despite aggressive treatment. PATIENTS AND METHODS We herein report the clinical findings of two unrelated cases of CACT deficiency with mutation confirmation, and in vitro bezafibrate responses using in vitro probe acylcarnitine (IVP) assay. Patients 1 and 2 are products of nonconsanguineous parents. Both patients developed cardiac arrest at day 3 of life but survived the initial events. Their blood chemistry revealed hypoglycemia and metabolic acidosis. The acylcarnitine profiles in both patients demonstrated increased long-chain acylcarnitines, suggesting CACT or carnitine palmitoyltransferase-2 (CPT2) deficiency. RESULTS The mutation analysis identified homozygous IVS2-10T>G in the SLC25A20 gene in both patients, confirming the diagnosis of CACT deficiency. The IVP assay revealed increased C16, C16:1, but decreased C2 with improvement by bezafibrate in the cultured fibroblasts. The short-term clinical trial of bezafibrate in Patient 1 did not show clinical improvement, and died after starting the trial for 6 months. CONCLUSION This splicing mutation has been identified in other Asian populations indicating a possible founder effect. IVP assay of cultured fibroblasts could determine a response to bezafibrate treatment. A long-term clinical trial of more enrolled patients is required for evaluation of this therapy.

Amino acid disorders detected by quantitative amino acid HPLC analysis in Thailand: An eight-year experience

BACKGROUND Amino acid disorders are a major group of inborn errors of metabolism (IEM) with variable clinical presentations. This study was aimed to provide the data of amino acid disorders detected in high-risk Thai patients referred to our metabolic lab from all over the country. METHODS From 2001 to 2009, we analyzed amino acids by HPLC in 1214 plasma and cerebrospinal fluid specimens. These specimens were obtained from patients with clinical suspicion of IEM or with positive newborn screening. The clinical data of the patients with confirmed diagnoses of amino acid disorders were also analyzed. RESULTS Fifty-eight patients were diagnosed with amino acid disorders, including 20 cases (34.5%) with maple syrup urine disease, 13 (22.4%) with phenylketonuria and hyperphenylalaninemia, 13 (22.4%) with nonketotic hyperglycinemia, 9 (15.5%) with urea cycle defects, 2 (3.4%) with classical homocystinuria, and 1 (1.7%) with ornithine aminotransferase deficiency. There was considerable delay in diagnoses which led to poor outcomes in most patients. CONCLUSION The prevalence of amino acid disorders in Thailand is distinct from other countries. This will guide the selection of the prevalent IEM for the future expansion of newborn screening program in this country.