Childhood hypophosphatasia with myopathy: clinical report with recent update

Hypophosphatasia is a rare genetic disease with low tissue nonspeficic alkaline phosphatase activity (TNSALP), due to ALPL gene mutation. There are 6 clinical forms. Childhood form is caractherized by short stature, premature loss of decidous teeth and diffuse bone pain associated with a pathological bone fracture in the past. Laboratory findings present low serum level of alkaline phosphatase and high levels of serum and urinary extracelular metabolytes. It is described a case report of a 34 years old woman with previous diagnosis of childhood hypophosphatasia, caryotype 46,XX, and molecular screening for the gene ALPL with a c.1426>A p.E476K mutation, who complained of proximal muscular weakness intensified with the cold weather, exercise, and a waddling gait. The electromyography was compatible with myopathy but the muscle biopsy was normal. The serum creatine kinase levels were normal, as well as the others muscle enzymes. Clinical and laboratory/ /imaging dissociation is frequent in other metabolic bone diseases as osteomalacia. The rarity of this case of childhood hypophosphatasia with "de novo" non-progressive myopathy of the lower limbs, justified a case report with literature revision.