Longitudinal monitoring of bone mineral density in thalassemic patients. Genetic structure and osteoporosis

The changes in bone mineral density (BMD) measured by single photon absorptiometry (SPA) using two observations conducted over a period of 2 years were examined in 54 thalassemic subjects [ 30 F(A)and 24 M (B)] with a chronological age ranging from 2.6 to 22.6 years and in 27 sex- and age-matched controls (C). Each category (A. B and C) was divided into three groups according to pubertal signs: pre-pubertal subjects (A1, B1 and C1): peri-pubertal subjects (A2, B2 and C2) and pubertal subjects from the first observation (A3, B3 and C3). Furthermore, each group of patients was divided into sub-groups on the basis of haematological phenotypes, those with a more severe form were called β⁰/β⁰ while those with other forms were called "others". The most significant findings were the following: the presence of a more severe reduction of the bone mineral density in patients with the β⁰/β⁰ phenotype than in patients with the "others" phenotype; patients with hypogonadism corresponded to the β⁰/β⁰ phenotype, while those with spontaneous puberty corresponded to the "others" phenotype. In conclusion, since puberty and the degree of bone mineral density are related to the haematological phenotype, puberty (spontaneous or induced) positively influences the bone mineral density only at the start of puberty, while subsequently, the degree of osteoporosis is the expression of widespread and chronic systemic damage due to the haematological phenotype.