Treatment of hypophosphatasia

Effects of asfotase alfa on fracture healing of adult patient with hypophosphatasia and literature review

OBJECTIVE

Hypophosphatasia (HPP) is a rare inherited disorder caused by ALPL gene mutations, with fracture nonunion being a serious complication. This study investigated the effects of teriparatide and asfotase alfa (AA) on femoral fracture healing of an adult patient with HPP, accompanied with a literature review.

METHODS

A 37-year-old woman wheelchair-bound was diagnosed with HPP due to an extremely low serum alkaline phosphatase (ALP) level (4-10 U/L), who suffered from bilateral femur pain and non-union of femoral shaft fractures on both sides. Compound heterozygous missense mutations (c.382G > A and c.461C > T) were identified in exon5 of ALPL gene. The patient received teriparatide sequential AA therapy. Serum levels of ALP, β-isomerized carboxy-telopeptide of type I collagen (β-CTX) and procollagen type 1 amino-terminal peptide (P1NP), bone mineral density (BMD) and skeletal X-ray were measured during the treatment. Literature was searched by keywords of "Hypophosphatasia", "HPP", "ALPL", "TNSALP", "ALP" combined with "Asfotase alfa", "AA", "enzyme replacement therapy", and "ERT".

RESULTS

After unsuccessful 6-month teriparatide treatment for femoral fracture, AA treatment was initiated, at a dose of 2 mg/kg, 3 times a week. After the first month of AA treatment, serum ALP level increased from 4 to 9206 U/L, and serum calcium and phosphate levels decreased, with increase in PTH, β-CTX, and P1NP levels. After 4 months of AA treatment, her bone pain significantly alleviated, accompanied by significant shortening of the fracture line. After 10 months of AA therapy, the fracture demonstrated complete healing and the patient could walk independently. BMD at lumbar spine and hips was significantly increased. Among 295 adult patients with HPP reported in the literature, 213 (72.2%) exhibited skeletal-related symptoms and 91 (30.8%) presented with bone fractures. In addition to skeletal manifestations, the patients presented with early tooth loss, muscle weakness and ectopic calcification. AA treatment, spanning 9 weeks to 3 years, has been shown to increase ALP levels, promote fracture healing, improve mobility, and alleviate bone pain.

CONCLUSION

Adult HPP patients mainly present with recurrent or poorly healing fractures, bone pain, and early loss of teeth. AA replacement therapy can effectively promote fracture healing, relieve bone pain, and enhance mobility.

Diagnosis, treatment, and follow-up of patients with hypophosphatasia

INTRODUCTION

Hypophosphatasia is a rare inherited systemic metabolic disorder, with an estimated prevalence in the severe forms of the disease of 1/100.000-1/300.000, that affects the typical architecture of bone, leading to defective mineralization during growth and remodeling. It is characterized by loss-of-function variants in the ALPL gene, resulting in low activity of tissue-nonspecific alkaline phosphatase. In severe cases, it can be fatal.

OBJECTIVE

To generate recommendations on the diagnosis, treatment, and follow-up of patients with hypophosphatasia based on available evidence.

MATERIALS AND METHODS

A search for evidence published between 2012 and 2024 was carried out in Medline and Embase. The search was expanded with information from various sources, including official sites of development groups, consensuses, technology evaluations, Google Scholar, clinical experts, and reference lists. The quality of the evidence was evaluated according to the type of document type. A modified Delphi consensus process was carried out with external experts, apart from the development group, it was established an 80% agreement threshold to define the final recommendations.

RESULTS

Sixty-one papers were found in the evidence search. The global quality of the evidence was low. In addition, a consensus was reached on 94 recommendations regarding diagnosis, treatment, and follow-up. Those recommendations were approved by external clinical experts from Colombia, Argentina, Spain, and Mexico.

CONCLUSIONS

The recommendations proposed in this document are based on the evidence available to the date the search was carried out, and the judgment of clinical experts. The recommendations on diagnosis, treatment, and follow-up are expected to guide the daily clinical practice for patients with HPP.

A Case of Hypophosphatasia Started Enzyme Replacement Therapy Since Babyhood Stage

BACKGROUND

Hypophosphatasia (HPP) is an inherited disease caused by low activity of tissue-nonspecific alkaline phosphatase. Dental characteristics include premature loss of primary teeth, enlarged pulp chambers, and enamel hypoplasia. Although enzyme replacement therapy with asfotase alfa was approved in 2015, there are few reports about the dental outcomes of this treatment.

CASE PRESENTATION

A 1-year-old girl referred to our hospital had already lost two primary teeth at the time of her initial visit. She started enzyme replacement therapy 6 days after birth, and genetic analysis later confirmed the diagnosis of HPP. At the age of 4 years and 7 months, 11 primary teeth had been lost, and some of the exfoliated teeth showed inflammatory root resorption or root fracture. There was also a history of abscess formation in a non-carious primary molar.

CONCLUSIONS

This report suggests that early enzyme replacement therapy may prevent traditional tooth loss in patients with HPP. It also highlights the new challenges posed for dental professionals in providing infection control in large pulp cavities and receding periodontal tissue.

Modern Approaches to the Management of Children with Hypophosphatasia

Hypophosphatasia is rare genetic disease caused by tissue-nonspecific alkaline phosphatase deficiency due to the mutation in the ALPL gene. Disease can manifest in utero, in childhood or in adults depending on its form and severity. This article presents modern data on the epidemiology, etiology, and clinical signs of hypophosphatasia in children, covers in details differential diagnostic search, and gives guidelines for its evidence-based treatment. Without timely treatment the prognosis of the disease is unfavorable in most cases. Such patients require follow-up by multidisciplinary team of physicians. The only effective method of treatment is enzyme replacement therapy with asfotase alfa. Symptomatic therapy is also crucial as well as physiotherapeutic procedures and therapeutic exercise programs (at rehabilitation stage).