The symptoms caused by the early stages of the disease are not pathognomonic and include anorexia, fatigue, weight loss or a developmental arrest in younger children.
[symptoma.com]
[…] are due to disrupted hematopoiesis with ensuing Anemia Thrombocytopenia Granulocytopenia Anemia can manifest with fatigue, weakness, pallor, malaise, dyspnea on exertion, tachycardia
[msdmanuals.com]
[…] days 2, 3 level 3, days 4, 5 level 4 Neutropenia grade 3 (1%) or 4 (93%), infection grade 3 (57%), 4 (14%), or 5 (8%), thrombocytopenia grade 4 (85%), stomatitis (66%), anorexia
[ufrgs.br]