Impressive clinical improvement and disappearance of neuropathic pain in an adult patient with hypophosphatasia treated with asfotase alfa.

Hypophosphatasia (HPP) is a rare disorder, resulting from loss-of-function variants of the ALPL gene encoding non-tissue specific alkaline phosphatase (TNSALP). Presentation varies largely, with increased severity usually occurring with earlier disease onset. Here we describe the clinical improvement of a 57-year-old woman with childhood onset HPP, after initiating treatment with asfotase alfa (Strensiq®). This was started because of the rapid and progressive radiological deterioration of bone structure after placement of nails in both upper legs for spontaneous atypical femur fracture (AFF) - like fractures. Initiation of treatment, not only resulted in stabilization of bone structure on X-rays, but within a few weeks there was a dramatic reduction of burning pain sensations in the lower legs, attributed in retrospect to neuropathic pain, and also almost complete disappearance of headaches. Additionally, unhealed metatarsal fractures finally healed after almost 10 years. Drug efficacy was further evaluated through -quality of life questionnaires and multiple tests conducted by the physiotherapist, and showed clear improvements. Within 3 months after starting asfotase alfa, the patient was able to carry out her daily tasks indoors without relying on a walker and even started electric bike rides for 20 km/day. In conclusion, treatment with asfotase alfa, halted rapid radiological bone deterioration after bilateral intramedullary femoral pen placement and strongly increased quality of life, marked by rapid disappearance of neuropathic pain, reduction in headaches and musculoskeletal pains, and enhanced muscle strength and mobility. The quick and almost complete disappearance of neuropathic pain and headache suggests a relation with disturbed levels of metabolites in HPP.

Study on genetic etiology of two cases with hypophosphatasia(HPP) using whole-exome sequencing / 中华内分泌代谢杂志

Objective:Clinical and genetic analysis were conducted in 2 patients with hypophosphatasia(HPP) and their families to explore the pathogenic mechanism of HPP.Methods:The genomic DNA was extracted from peripheral blood of two patients with HPP and their family members. Sanger sequencing and pedigree verification were performed on the pathogenic variants identified using whole-exome sequencing. Then the function of the mutation sites was analyzed with bioinformatics software.Results:Proband 1 presented with developmental retardation, pectus funnel and premature loss of deciduous tooth, of which the serum alkaline phosphatase level was slightly lower than the bound of the normal range. Two complex heterozygous missense variants c. 1120G>A and c. 1334C>G of ALPL gene were detected in the proband 1 which were inherited from his parents respectively, showing an autosomal recessive inheritance. Both the variants were predicted to inflict deleterious effects on ALPL gene function by multiple bioinformatics program, and were classified as likely pathogenetic variants according to American College of Medical Genetics and Genomics(ACMG) guidelines. Proband 2 showed three missing permanent teeth and the significantly lower level of serum alkaline phosphatase than normal range. A heterozygous variant c. 1190-3C>G of ALPL gene was detected in proband 2 whose pattern of inheritance was unknown. The clinical significance of this variant was unknown according to ACMG standards and guidelines. All of these variants were considered as novel since none of them has been reported. Along with the above combined results, proband 1 and 2 were diagnosed as childhood HPP and Odontohypophosphatasia, respectively.Conclusion:This study reinforced the relationship between HPP and variants in ALPL gene. Two variants, c. 1120G>A and c. 1334C>G, were located in the homodimer interface and crown domain of tissue-nonspecific alkaline phosphatase(TNSALP), respectively, while c. 1190-3C>G were located in the splice sites, which might result in low TNSALP activity.

Clinical and genetic analysis of a family with low alkaline phosphatase / 临床儿科杂志

Objective To investigate the role of TNSALP gene detection in prenatal diagnosis of HPP. Method The clinical data and the results of complete exon sequencing of TNSALP gene in one neonate with low alkaline phosphatase (HPP) were analyzed retrospectively. Peripheral bloods from his family members were collected. The amniotic fluid cell in fetuses at 17 weeks was tested for candidate gene mutations by Sanger sequencing. Results Mainly manifestations in 6-day-old baby were multiple fractures, limb shortening and bending and dyspnea. He died of respiratory failure 9 days after birth. The serum alkaline phosphatase was decreased and serum calcium was decreased slightly; serum phosphorus, serum 25 hydroxyvitamin-D and parathyroid hormone were normal. X-ray showed that the whole body bone was very poorly mineralized, and the long diaphysis was enlarged with shape of a cup at the end and multiple fractures existed. Gene sequencing revealed a complex heterozygous missense mutation in the TNSALP gene, including the heterozygous missense mutation c.542C>T in exon sixth causing 181st amino acids changed from serine to leucine (p.S181L), and tenth exon heterozygous missense mutation in c.1016G>A causing 339th amino acid changed from glycine to glutamic acid (p.G339E). The parental phenotypes were normal. The c.542C>T mutation is inherited from his father and the c.1016G>A mutation is inherited from his mother. These two mutations were not detected in the fetus. Conclusion TNSALP gene analysis can be applied to the diagnosis and prenatal diagnosis of HPP.