Rickets or osteomalacia is a metabolic bone disease in which the bone is not adequately mineralized, they are less rigid, they become deformed and incomplete fractures (fissures) appear, especially in the long bones, especially in the legs, since they have to carry loads. the weight. “We talk about rickets when it affects children, and osteomalacia when it affects adults.
Although there are different causes, in times of famine (low protein and dairy intake and little sun exposure) outbreaks of deficiency rickets occur. Others are secondary to kidney diseases, and there are also genetic ones. The most common genetic type is X-linked hypophosphatemia (X-linked hypophosphatemia or XLH)”, explains Dr. Carlos Gómez Alonso, head of the Bone and Mineral Metabolism Clinical Management Unit of the Central University Hospital of Asturias .
What is XLH and who does it mainly affect?
Patients with XLH have a mutation in a gene (PHEX), which increases a hormone whose role under normal conditions is to regulate the metabolism of phosphate, which, along with calcium, is essential for bone mineralization. What happens in XLH is that more phosphate is excreted in the urine than it should, altered vitamin D metabolism, which can lead to growth retardation, bone deformities, fractures, and extreme muscle weakness.
Bone deformities alter the mechanical load on the joints, produce joint pain that, together with muscle weakness, makes them more prone to being obese due to decreased mobility and enters into a vicious circle that profoundly alters the quality of life.
This disease is transmitted genetically: mothers with XLH will transmit it to 50% of their children, regardless of gender; while parents will never transmit it to their sons and 100% of their daughters. There are also spontaneous mutations in which the disease appears without having inherited it from the parents.
How is this disease diagnosed?
In children, the most common is growth retardation. Once they begin to walk, deformities of the femurs and tibias (bow legs) appear along with muscle weakness and pain. A simple test, such as determining blood phosphate and checking for urinary phosphate loss, opens the door to differential diagnosis.
It can also be confirmed with a genetic diagnosis, essential if you are going to have offspring.
What are the diagnostic challenges faced by patients with XLH?
One of the main challenges is that it is not confused with deficiency rickets. In the past, these patients were labeled as vitamin D-resistant rickets, since they did not respond like deficient patients to treatment with vitamin D and calcium supplements.
Today, the main challenge for a child with XLH is for an early diagnosis and correct treatment to allow adequate growth, avoid bone deformities and prevent the appearance of the usual complications such as calcification of the kidneys or overstimulation of the parathyroid glands, which make it difficult to manage the disease.
Taking into account that it is a chronic and progressive disease, what are the symptoms and signs that patients with XLH present in adulthood?
It will depend on the severity of the disease and the management in childhood. Short stature, leg deformities, osteoarthritis in the hips and knees, calcifications, narrowing of the medullary canal, bone fractures or pseudofractures that take years to heal, muscle weakness, recurrent dental abscesses and loss of teeth, loss of hearing and a long etcetera.
All this is reflected in the deterioration of the quality of life, difficulties in carrying out work activities, obesity and psychological repercussions. Due to all these repercussions, a multidisciplinary approach is required.
What can we do to help make this disease visible?
It is always difficult to give visibility to a rare disease, with many symptoms that are very similar to common diseases. It's like finding the famous Wally on the crowded beach. In the case of XLH, it may be important to make visible the repercussions that adult patients have, with their burden of suffering, morbidity, and even decreased life expectancy, in addition to the socioeconomic burdens of the disease. At present, with adequate treatment, we can drastically reduce the burden of the disease in the future.
