Rare diseases

A disease is considered rare when it affects a small proportion of the population. In Europe, a disease is considered rare when the incidence is less than 5 cases per 10,000 inhabitants. There are about 7,000 rare diseases in the world and a high percentage (between 50% and 75%) affect the pediatric population. In general, rare diseases present diagnostic complexity (average time to obtain the diagnosis is 5 years) and most do not have an approved pharmacological therapy.

 

Renal tubular acidosis

• Renal tubular acidosis or RTA is a rare disease that groups 4 types:
• Distal renal tubular acidosis (type 1),
• proximal renal tubular acidosis (type 2),
• renal tubular acidosis type 3 (which shares characteristics of the two previous ones) and,
• renal tubular acidosis type 4 (this disease appears with a high potassium in the blood unlike the previous 3).
• In all of them, the bicarbonate in the blood is low, as is the blood pH, a situation called acidosis.

Distal renal tubular acidosis (type 1) is a rare disease estimated to affect 4.8 people per million inhabitants. It is characterized by low blood pH, high blood chlorine, and low potassium. There is excess calcium (hypercalciuria) and low citrate (hypocitraturia) in the urine, with the pH of the urine being higher than usual. Hypercalciuria, hypocitraturia and elevated pH in urine are 3 factors that lead to the formation of calcium phosphate deposits in the kidney structure (nephrocalcinosis) as well as the formation of stones in the kidney and in the urinary tract (nephrolithiasis). Low potassium in the blood can in some cases induce some type of cardiac arrhythmia and muscle weakness. Poorly corrected metabolic acidosis (low pH in the blood) can lead to osteoporosis, bone deformities, growth retardation, and short stature. Deafness may occur in some patients, depending on the specific type of genetic alteration that the patient presents. Distal renal tubular acidosis can be classified into two types: 1) primary or hereditary (existence of an abnormal gene) 2) acquired or secondary to another disease. Secondary forms are undoubtedly the most frequent. Among the causes that can generate it are certain autoimmune diseases, primary hyperparathyroidism, administration of certain drugs, or other circumstances.

The treatment of this disease consists of correcting the low blood pH and the potassium also decreased. Alkalizing salts are administered orally to achieve that goal. The combination of potassium citrate/potassium bicarbonate in microtablets is presented as the only therapeutic alternative with an approved indication for the treatment of said disease.