George E. Tiller

Enzyme-replacement therapy in mucopolysaccharidosis I.

BACKGROUND Mucopolysaccharidosis I is a lysosomal storage disease caused by a deficiency of the enzyme alpha-L-iduronidase. We evaluated the effect of enzyme-replacement therapy with recombinant human alpha-L-iduronidase in patients with this disorder. METHODS We treated 10 patients with mucopolysaccharidosis I (age, 5 to 22 years) with recombinant human alpha-L-iduronidase at a dose of 125,000 U per kilogram of body weight given intravenously once weekly for 52 weeks. The patients were evaluated at base line and at 6, 12, 26, and 52 weeks by detailed clinical examinations, magnetic resonance imaging of the abdomen and brain, echocardiography, range-of-motion measurements, polysomnography, clinical laboratory evaluations, measurements of leukocyte alpha-L-iduronidase activity, and urinary glycosaminoglycan excretion. RESULTS Hepatosplenomegaly decreased significantly in all patients, and the size of the liver was normal for body weight and age in eight patients by 26 weeks. The rate of growth in height and weight increased by a mean of 85 and 131 percent, respectively, in the six prepubertal patients. The mean maximal range of motion of shoulder flexion and elbow extension increased significantly. The number of episodes of apnea and hypopnea during sleep decreased 61 percent. New York Heart Association functional class improved by one or two classes in all patients. Urinary glycosaminoglycan excretion decreased after 3 to 4 weeks of treatment; the mean reduction was 63 percent of base-line values. Five patients had transient urticaria during infusions. Serum antibodies to alpha-L-iduronidase were detected in four patients. CONCLUSIONS In patients with mucopolysaccharidosis I, treatment with recombinant human alpha-L-iduronidase reduces lysosomal storage in the liver and ameliorates some clinical manifestations of the disease.

Identification of the gene (SEDL) causing X-linked spondyloepiphyseal dysplasia tarda

Spondyloepiphyseal dysplasia tarda (SEDL; MIM 313400) is an X-linked recessive osteochondrodysplasia that occurs in approximately two of every one million people. This progressive skeletal disorder which manifests in childhood is characterized by disproportionate short stature with short neck and trunk, barrel chest and absence of systemic complications. Distinctive radiological signs are platyspondyly with hump-shaped central and posterior portions, narrow disc spaces, and mild to moderate epiphyseal dysplasia. The latter usually leads to premature secondary osteoarthritis often requiring hip arthroplasty. Obligate female carriers are generally clinically and radiographically indistinguishable from the general population, although some cases have phenotypic changes consistent with expression of the gene defect. The SEDL gene has been localized to Xp22 (Refs 8,9) in the approximately 2-Mb interval between DXS16 and DXS987 (ref. 10). Here we confirm and refine this localization to an interval of less than 170 kb by critical recombination events at DXS16 and AFMa124wc1 in two families. In one candidate gene we detected three dinucleotide deletions in three Australian families which effect frameshifts causing premature stop codons. The gene designated SEDL is transcribed as a 2.8-kb transcript in many tissues including fetal cartilage. SEDL encodes a 140 amino acid protein with a putative role in endoplasmic reticulum (ER)-to-Golgi vesicular transport.

Marshall Syndrome Associated with a Splicing Defect at the COL11A1 Locus

Marshall syndrome is a rare, autosomal dominant skeletal dysplasia that is phenotypically similar to the more common disorder Stickler syndrome. For a large kindred with Marshall syndrome, we demonstrate a splice-donor-site mutation in the COL11A1 gene that cosegregates with the phenotype. The G+1-->A transition causes in-frame skipping of a 54-bp exon and deletes amino acids 726-743 from the major triple-helical domain of the alpha1(XI) collagen polypeptide. The data support the hypothesis that the alpha1(XI) collagen polypeptide has an important role in skeletal morphogenesis that extends beyond its contribution to structural integrity of the cartilage extracellular matrix. Our results also demonstrate allelism of Marshall syndrome with the subset of Stickler syndrome families associated with COL11A1 mutations.

Isolation and characterization of a mammalian homolog of the Drosophila white gene.

The Drosophila melanogaster white gene is a member of the ABC transporter superfamily of ATPase transmembrane proteins and is involved in the cellular uptake of guanine and tryptophan. We have cloned and sequenced human and mouse homologs of white which share 55-58% amino acid similarity with the Drosophila protein. Northern analysis reveals that the mammalian homolog is highly expressed in several tissues, including brain, spleen, lung and placenta. We have localized the gene to human chromosome 21q22.3 by means of fluorescence in situ hybridization and linkage analysis using a (CA)n polymorphism. The human homolog maps to the interval between D21S212 and D21S171, a region which includes loci for bipolar affective disorder and a recessive form of deafness. Since tryptophan is a precursor for the neurotransmitter serotonin and neurotoxic metabolites of the kynurenine pathway, we propose that the human homolog of white is a suitable candidate gene for these neurological disorders in humans.

The Molecular Basis of X-Linked Spondyloepiphyseal Dysplasia Tarda

The X-linked form of spondyloepiphyseal dysplasia tarda (SEDL), a radiologically distinct skeletal dysplasia affecting the vertebrae and epiphyses, is caused by mutations in the SEDL gene. To characterize the molecular basis for SEDL, we have identified the spectrum of SEDL mutations in 30 of 36 unrelated cases of X-linked SEDL ascertained from different ethnic populations. Twenty-one different disease-associated mutations now have been identified throughout the SEDL gene. These include nonsense mutations in exons 4 and 5, missense mutations in exons 4 and 6, small (2-7 bp) and large (>1 kb) deletions, insertions, and putative splicing errors, with one splicing error due to a complex deletion/insertion mutation. Eight different frameshift mutations lead to a premature termination of translation and account for >43% (13/30) of SEDL cases, with half of these (7/13) being due to dinucleotide deletions. Altogether, deletions account for 57% (17/30) of all known SEDL mutations. Four recurrent mutations (IVS3+5G-->A, 157-158delAT, 191-192delTG, and 271-275delCAAGA) account for 43% (13/30) of confirmed SEDL cases. The results of haplotype analyses and the diverse ethnic origins of patients support recurrent mutations. Two patients with large deletions of SEDL exons were found, one with childhood onset of painful complications, the other relatively free of additional symptoms. However, we could not establish a clear genotype/phenotype correlation and therefore conclude that the complete unaltered SEDL-gene product is essential for normal bone growth. Molecular diagnosis can now be offered for presymptomatic testing of this disorder. Appropriate lifestyle decisions and, eventually, perhaps, specific SEDL therapies may ameliorate the prognosis of premature osteoarthritis and the need for hip arthroplasty.

Nephrotic Syndrome Complicating α-Glucosidase Replacement Therapy for Pompe Disease

We report a patient with Pompe disease who developed reversible nephrotic syndrome during prolonged, high-dose, experimental, enzyme replacement therapy with recombinant human acid α-glucosidase (rhGAA). Because of the development of antibodies to rhGAA and concomitant clinical decline, escalating doses of rhGAA were administered as part of an experimental immune tolerance regimen. Histologic evaluation of kidney tissue revealed glomerular deposition of immune complexes containing rhGAA itself, in a pattern of membranous nephropathy. To our knowledge, this is the first reported case of nephrotic syndrome occurring during enzyme replacement therapy. The nephrotic syndrome gradually resolved after the rhGAA dose was decreased, indicating that decreasing the antigenic load can ameliorate glomerular immune complex deposition associated with enzyme replacement in a highly sensitized patient.

Safety and efficacy of enzyme replacement therapy in combination with hematopoietic stem cell transplantation in Hurler syndrome

Purpose: Hurler syndrome is a debilitating genetic disease with a typical life span of 5 to 8 years. Early hematopoietic stem cell transplantation (HSCT) mitigates disease symptoms and improves survival. However, morbidity and mortality associated with HSCT can limit its success. We describe the initial experience with combined use of enzyme replacement therapy (ERT, laronidase) and HSCT in Hurler syndrome.Methods: Thirteen transplants were performed in 12 patients. ERT was given at a standard dose of 0.58 mg/kg per week. Transplant conditioning regimen and donor graft source were determined by institutional protocol.Results: The median age at initiation of ERT was 12 months (range, 8 to 18 months). The median duration of pre-HSCT ERT was 12 weeks (range, 4 to 28). All but 1 patient tested showed decrease in urinary GAG excretion during ERT. ERT infusion-related toxicity was limited to mild reactions. Development of antibodies to laronidase did not correlate with infusion reactions or responses in urinary GAG excretion. ERT was given for a median of 7 weeks (range, 3 to 20) after HSCT. After transplantation, eight patients demonstrated complete donor engraftment and four suffered graft failure. Two patients required ventilator support and three developed acute GVHD. Eleven of the 12 patients are surviving with a median follow-up of 3 months (range, 1 to 7 months).Conclusions: In children with Hurler syndrome, ERT with HSCT is feasible and well tolerated. Development of antibodies against exogenous enzyme does not appear to correlate with infusion reactions or response to ERT. A prospective study is needed to determine the effect of concomitant ERT on transplant outcomes.

A Recurrent RNA-Splicing Mutation in the SEDL Gene Causes X-Linked Spondyloepiphyseal Dysplasia Tarda

Spondyloepiphyseal dysplasia tarda (SEDL) is a genetically heterogeneous disorder characterized by mild-to-moderate short stature and early-onset osteoarthritis. Both autosomal and X-linked forms have been described. Elsewhere, we have reported the identification of the gene for the X-linked recessive form, which maps to Xp22.2. We now report characterization of an exon-skipping mutation (IVS3+5G-->A at the intron 3 splice-donor site) in two unrelated families with SEDL. Using reverse transcriptase (RT)-PCR, we demonstrated that the mutation resulted in elimination of the first 31 codons of the open reading frame. The mutation was not detected in 120 control X chromosomes. Articular cartilage from an adult who had SEDL and carried this mutation contained chondrocytes with abundant Golgi complexes and dilated rough endoplasmic reticulum (ER). RT-PCR experiments using mouse/human cell hybrids revealed that the SEDL gene escapes X inactivation. Homologues of the SEDL gene include a transcribed retropseudogene on chromosome 19, as well as expressed genes in mouse, rat, Drosophila melanogaster Caenorhabditis elegans, and Saccharomyces cerevisiae. The latter homologue, p20, has a putative role in vesicular transport from ER to Golgi complex. These data suggest that SEDL mutations may perturb an intracellular pathway that is important for cartilage homeostasis.

Chondrodysplasia punctata associated with maternal autoimmune diseases: Expanding the spectrum from systemic lupus erythematosus (SLE) to mixed connective tissue disease (MCTD) and scleroderma report of eight cases†

Chondrodysplasia punctata (CDP) is etiologically a heterogeneous condition and has been associated with single gene disorders, chromosome abnormalities and teratogenic exposures. The first publication of the association between CDP and maternal autoimmune connective tissue disorder was by Curry et al. 1993 ]. Chondrodysplasia punctata associated with maternal collagen vascular disease. A new etiology? Presented at the David W. Smith Workshop on Morphogenesis and Malformations, Mont Tremblant, Quebec, August 1993] and subsequently, other cases have been reported. We report on eight cases of maternal collagen vascular disease associated with fetal CDP and included the cases reported by Curry et al. 1993 . Chondrodysplasia punctata associated with maternal collagen vascular disease. A new etiology? Presented at the David W. Smith Workshop on Morphogenesis and Malformations, Mont Tremblant, Quebec, August 1993] and Costa et al. [1993]. Maternal systemic lupus erythematosis (SLE) and chondrodysplasia punctata in two infants. Coincidence or association? 1st Meeting of Bone Dysplasia Society, Chicago, June 1993] which were reported in an abstract form. We suggest that maternal autoimmune diseases should be part of the differential diagnosis and investigation in newborns/fetuses with CDP. Thus, in addition to cardiac evaluation, fetuses/newborn to mothers with autoimmune diseases should have fetal ultrasound/newborn examination and if indicated, X‐rays, looking for absent/hypoplastic nasal bone, brachydactyly, shortened long bones and epiphyseal stippling.

Aortic root dilatation in Ehlers-Danlos syndrome types I, II and III A report of five cases

We have identified five families in whom individuals affected with the Ehlers‐Danlos syndrome (EDS) types I, II or III had aortic root dilatation (ARD). All propositi had a low upper/lower segment ratio but no other diagnostic skeletal or ocular features of Marfan syndrome. Their skin had the soft, velvety texture characteristic of EDS and all had significant joint laxity. Probands included a 4‐year‐old girl with EDS type I, 4‐and 8‐year‐old girls with EDS type HI, a 35‐year‐old male with EDS type II, and a 51‐year‐old female with EDS type III. Review of these cases suggests the need for multicenter clinical studies in order to determine the prevalence and the rate of progression of ARD in EDS types I, II, and III. Such studies are necessary to determine whether echocardiograms (including measurement of aortic root diameter) should be considered on initial evaluation of all patients with mild forms of EDS.