We previously demonstrated that the mutations Met1Val (M1V) and the deletion of nucleotides 1484-1490 (1484-1490del) in Dentin matrix protein-1 (DMP1) cause the novel disorder autosomal recessive hypophosphatemic rickets (ARHR), which is associated with elevated Fibroblast growth factor-23 (FGF23). To further understand the role of DMP1 in ARHR, we undertook molecular genetic and in vitro expression studies. First, we examined a kindred with a severe hypophosphatemic rickets phenotype and recessive inheritance. Analyses of this family demonstrated that the affected members had elevated serum FGF23 and carried a large, biallelic deletion that removed the majority of DMP1. At a minimum, this deletion encompassed 49 kb between DMP1 exon 3 and an intergenic region 5′ to the next telomeric gene, integrin-binding sialoprotein (IBSP). We next performed immunofluorescent studies in cells to understand the effects of the known ARHR mutations on DMP1 cellular processing. These analyses showed that the M1V DMP1 mutant was not sorted to the transGolgi network (TGN) and secretory pathway, but filled the entire cytoplasm. In contrast, the 1484-1490del mutant localized to the TGN and was secreted, similar to wild type DMP1. The 1484-1490del mutation replaces the DMP1 18 C-terminal amino acids with 33 non-native residues. Truncation of wild type DMP1 by these native 18 residues followed by Western blot and confocal microscopic analyses demonstrated a wild type expression pattern when compared with the 1484-1490del mutant, indicating that the last 18 residues are not critical for cellular trafficking, but that the 33 additional residues arising from the 1484-1490del mutation likely compromise DMP1 processing. The relationship between DMP1 and FGF23 is unclear. To test endogenous DMP1 response to serum metabolites that also regulate FGF23, UMR-106 cells were treated with 1,25 (OH) 2 vitamin D (1×10 −7 M) and showed a 12-fold increase in DMP1 mRNA and protein at 24 hr. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptBone. Author manuscript; available in PMC 2010 February 1. In summary, we have identified a novel DMP1 deletion as the cause of ARHR, as well as demonstrated that the ARHR mutations alter DMP1 cellular processing, and that DMP1 can be regulated by vitamin D. Taken together, this work expands our understanding of the genetic and molecular mechanisms associated with DMP1 alterations causing ARHR.

IV zoledronic acid is an effective and well-tolerated treatment to prevent bone mineral density loss at the total hip and trochanter for up to 12 months following SCI.

Hypophosphatasia is a rare inherited disease caused by a loss of function mutations in the gene that codes for the tissue-nonspecific alkaline phosphatase enzyme. It is autosomally inherited and at least 388 different genetic defects have been identified. The clinical presentation is variable from a severe perinatal form, that is fatal if untreated, to adult-onset disease. This review covers the pathophysiology, diagnosis and current management option including the recently licensed enzyme replacement therapy asfotase alfa.

Background X-linked hypophosphatemia (XLH) is a rare, genetic phosphate-wasting disease resulting in bone, muscular and dental problems, beginning in childhood and increasing in adulthood. This qualitative analysis aimed to explore patient-reported symptoms, complications and experiences of XLH over the life-course, using data from a large multinational online survey. Methods Responses to two open-ended questions from 209 adults and 86 children/adolescents (proxy report) with self-reported XLH were analyzed in eight age groups. Two researchers independently coded and analyzed the responses, using thematic analysis, with differences settled among a multi-disciplinary group. Six themes were identified, with age sub-group analysis conducted on the three most common, according to coding frequency. Results Within theme 1, ‘Clinical Signs and Symptoms of XLH’, ‘Pain’ was a dominant sub-theme across the life-course, but ‘Skeletal Pathology’ dominated the responses of children/adolescents. Within theme 2, ‘Impacts of Clinical Signs and Symptoms’, interference with ‘Physical Exertion’ and ‘Emotional Wellbeing’ (comprising depression/anxiety in adults and lack of self-esteem in children/adolescents) was reported across all ages. For theme 3, ‘Negative Treatment Experiences’, ‘Medication’ was problematic for children, with adults reporting lack of ‘Access to Appropriate Treatment’. Three further themes were identified: ‘Resilience’, ‘Positive Treatment Experiences’, and ‘Information Needs.’ Conclusion The multiple burdens imposed on people with XLH throughout their lifetime encompassed the physical, emotional and social, although the most challenging symptoms or complications differed between ages. Burden was further exacerbated by adult’s lack of access to appropriate treatment, illustrating the need for age-appropriate multidisciplinary care.

Background: Fibrodysplasia ossificans progressiva (FOP), an ultra-rare disorder caused by mutations in the gene encoding activin A receptor type 1 (ACVR1), is characterized by painful flare-ups and cumulative heterotopic ossification (HO). Garetosmab, a fully-human monoclonal antibody blocking activin A, prevents HO in FOP mice. Methods: LUMINA-1 (NCT03188666) was a phase 2, multi-center, randomized, double-blind, placebo-controlled study evaluating the safety, tolerability, and effects on HO of intravenous (IV) garetosmab 10 mg/kg every 4 weeks (Q4W). Adult patients with FOP were randomized to garetosmab or placebo for 28 weeks (Period 1), followed by an open-label period (Period 2). After Period 2, patients were allowed to stay on garetosmab in an open-label extension. For Period 1, primary endpoints were HO total lesion activity (HO-TLA) by 18F-sodium fluoride positron emission tomography (18F-NaF PET) and HO total lesion volume by computed tomography (CT). The Period 2 primary endpoint compared the number of new lesions in Period 2 versus Period 1. The safety primary endpoint was incidence and severity of TEAEs through the end of the Period 1 at week 28. Findings: Patients (n=44) were randomized to garetosmab (n=20) or placebo (n=24). In Period_1, there was a trend for garetosmab to decrease HO-TLA versus placebo (24.6%; P=0.07), primarily driven by near complete prevention of new lesions (97% decrease by 18F-NaF PET, post-hoc P=0.009; 90% relative reduction by CT, post-hoc P=0.017); flare-ups were significantly reduced (P=0.0005). For placebo patients transitioning to garetosmab in Period 2, no patients developed new HO lesions (0% in Period 2 versus 40.9% in Period_1; P=0.0027) by CT. All 44 patients met primary safety endpoint of at least one TEAE during Period 1. Garetosmab was associated with more adverse events than placebo: mild recurrent epistaxis, madarosis, and skin/soft tissue infections. Overall, the AEs were predominantly mild in severity, with no effect on patients' ability to receive garetosmab. Five deaths (5/44; 11.4%) occurred either in Period 2 or the open-label extension. The deaths were associated with baseline disease severity in some, pre-existing comorbidities in others and occurred following 8-16 doses (median: 15) of garetosmab in the open label/follow-up periods. Interpretation: Garetosmab reduced flare-ups and prevented new HO lesions in FOP patients. Although side effects were mild to moderate, there were a relatively high number of deaths for a small study; the deaths were not related to epistaxis and considered unlikely to be related to garetosmab.