In this study we report reprogramming and generation of a new human induced pluripotent stem cell line UOMi009_A, which was generated from a 64 year old male patient with childhood onset Hypophosphatasia (HPP). The patient has compound heterozygous mutations in the ALPL gene (c.571G>A (p.Glu191Lys) and c.1001G>A (p.Gly334Asp)) which were confirmed in the UOMi009_A line. This line was well characterized and will help in our future assessment of HPP disease pathophysiology and drug screening.

The last decade has been revolutionary regarding the management of rare bone diseases caused by impaired calcium and phosphate metabolism. Elucidation of the underlying genetic basis and pathophysiologic alterations has been the determinant factor for the development of new, disease-specific treatment agents. The phosphaturic hormone Fibroblast Growth Factor 23 (FGF23) possesses a critical role in the pathogenesis of various hypophosphatemic disorders. Among them, the genetic disorder of X-linked hypophosphatemia and the acquired syndrome of tumor-induced osteomalacia, although very rare, have attracted the scientific community's attention towards designing an FGF23-inhibitor as a potential specific therapy. The monoclonal antibody burosumab was approved for the treatment of children and adult patients with X-linked hypophosphatemia and recently for tumor-induced osteomalacia patients, demonstrating benefits regarding their symptoms, biochemical profile and bone mineralization status. Asfotase alfa is a hydroxyapatite-targeted recombinant alkaline phosphatase, an enzymatic replacement therapy, substituting the defective activity of tissue non-specific alkaline phosphatase, in patients suffering from hypophosphatasia. Promising data regarding its favorable effect on survival rate, bone quality, fracture healing, muscle strength, mobility, respiratory function, and general quality of life have led to the approval of the drug for the treatment of childhood-onset hypophosphatasia. Given the high costs of treatment for both agents and their limited clinical use until now, more data are needed to define patients' characteristics that make them ideal candidates for therapy. Long-term safety issues also need to be clarified.

Hypophosphatasia (HPP) is a rare disorder resulting from biallelic loss-of-function variants or monoallelic dominant negative variants in the ALPL gene. We herein describe the clinical outcome of a 32-year-old woman with childhood-onset HPP caused by compound heterozygous variants in ALPL. Her chief complaints were severe musculoskeletal pain, muscle weakness, and impaired daily activities necessitating assistance in housework and child-rearing in addition to a history of early tooth loss and mildly short stature. Asfotase alfa therapy produced a remarkable increase in muscle strength and daily activities and markedly reduced musculoskeletal pain. Drug efficacy was clearly demonstrated through multiple test batteries (muscle strength test using microFET®2, six-minute walking test, Stair Climb Test, rising-from-floor-time test, and number-of-steps test using Actigraph®) currently adopted as standardized evaluations in Duchenne muscular dystrophy clinical trials since no test batteries for HPP have been established to date. These tests may also be promising for the assessment of HPP.

Hypophosphatasia is an inherited disease characterized by reduced alkaline phosphatase activity, extracellular accumulation of inorganic pyrophosphate, and impaired bone mineralization. Asfotase alfa (AA) is a recombinant human alkaline phosphatase therapy approved for treatment of pediatric-onset hypophosphatasia. Studies show promising outcome in AA-treated children with hypophosphatasia; however, data on adults with pediatric-onset hypophosphatasia are scarce. We report on a 59-year-old woman with childhood-onset hypophosphatasia and a history of multiple fractures and orthopedic procedures. Owing to renal failure (histological diagnosis: focal segmental glomerulosclerosis), hemodialysis was started in 2013. By the end of 2015, the patient was unable to walk, could only stand for 30 seconds, and was completely dependent on help for activities of daily living. After 13 months of AA therapy, the patient showed a dramatic increase in quality of life (increased mobility), reduction in pain medication, and a significant improvement in bone mineralization throughout the skeleton, including consolidation of existing fractures and no occurrence of new fractures. This case report demonstrates a relevant therapeutic success of AA treatment in an adult hemodialysis patient with childhood onset of hypophosphatasia.