Adult hypophosphatasia with a novel <i>ALPL</i> mutation: Report of an Indian kindred.

Abstract

Hypophosphatasia is an inborn error in metabolism characterized by low serum alkaline phosphatase (ALP) activity resulting from deactivating mutations in <i>TNSALP</i> (also known as <i>ALPL</i>), the gene that encodes the 'tissue-specific' isoenzyme of ALP. The disease exhibits significant clinical heterogeneity that spans from death <i>in utero</i> to only dental complications in adult life. Herein, we report a 47-year-old woman presenting with fracture of shaft of left femur. She had been complaining of pain in both of her thighs for the past 3 years. In addition, she gave a history of premature loss of teeth. Review of old radiographs revealed pseudo-fractures involving the lateral cortices of the femora on both sides. Biochemical panel revealed hyperphosphatemia, persistently low total alkaline phosphatase (ALP) and low-normal bone turnover markers. Screening of her siblings revealed low ALP in her younger sister and brother who were otherwise free from any major dento-arthro-osseous complaints. Sanger sequencing showed a novel, heterozygous, missense mutation in exon 5 at position 311 (c.311a > g;p.104 Asn > Ser) of <i>ALPL</i> gene in the three members. The patient underwent open reduction and intramedullary nailing of left femur along with prophylactic nailing on right side. This case report represents the first genetically confirmed kindred of adult hypophosphatasia from the Indian subcontinent.