1. Organic dysfunction (Number of organs affected (1, 2, 3, more than 3)). Measurement time: in the initial evaluation (day 1).
2. New dysfunction or progression of the previous one (Occurrence (yes or no), Degree of dysfunction (From 0 to 33 points)). Measurement time: in daily evaluations during admission to the PICU.
3. Degree of dysfunction (It will measure through the PELOD questionnaire). Measurement time: in the evaluations during admission to the PICU (Days 1, 2, 5, 8, 12, 16 and 18). If the patient leaves the PICU before any of those days, it is not evaluated.
4. New acquired infection (Occurrence (yes or no), classification (nosocomial or community)). Measurement time: daily evaluations during admission to the PICU, evaluations during treatment with BMT outside the PICU, evaluation at hospital discharge, Final evaluation (2 months).
5. Occurrence of complications (yes or no), Measurement time: daily evaluations during admission to the PICU, Evaluations during treatment with BMT outside the PICU, Evaluation at hospital discharge, Final Evaluation (2 months).
6. PICU stay (days), Measurement time: final evaluation (2 months).
7. Hospital stay (days).Measurement time: final evaluation (2 months).
8 Re-entry within 28 days (Occurrence (yes or no), cause (infectious or non-infectious)). Measurement time: final evaluation (2 months).
9. Nutritional status (Body Mass Index). Measurement time: initial evaluation, evaluation at hospital discharge and final evaluation (2 months).
10. Thymic Area (size in mm2). Measurement time: initial and, final evaluation (2 months).
11. CD4 + count (expressed in cel / µL and in%.). Measurement time: initial and, final evaluation (2 months).
12. Quantification of Immunoglobulins (IgA, IgM, IgG). Measurement time: initial and, final evaluation (2 months).
13. Vital signs (Blood pressure, heart rate, respiratory rate, temperature, oxygen saturation). Measurement time: in evaluations during treatment with BMT, before each administration and 1 h after them.
14. Adverse events (Occurrence (yes or no), Type (describe), Location (local or systemic), Time of appearance (minutes or hours), Duration (hours, minutes or days), Previous knowledge (expected or unexpected), Intensity (mild, moderate or severe), Consequence (severe or not serious), Causal relationship (Very probable / certain, Probable, Possible, Unlikely, Not related, Not evaluable / not classifiable)). Measurement time: in evaluations during BMT treatment, and, in the final evaluation (2 months).