Haemophilia A is a rare X-linked recessive bleeding disorder caused by deficiency or functional defects in coagulation factor VIII (FVIII). Here, we report two cases of challenging diagnosis of haemophilia A because of unusual presentation. The first case is a 10-month-old female, admitted to our hospital because a neck mass appeared within the previous 24 h, who had a past medical history consistent with recurrent spontaneous haematomas but no family history of bleeding disorders. Despite several radiological evaluations, only the histology of the mass defined the presence of a haematoma. Chromosomal analysis revealed a normal female karyotype and a de-novo mutation into the FVIII intron 22 associated with a skewed X chromosome inactivation. The second case is a male neonate with a history of seizures who underwent brain MRI that showed a suspicious vascular malformation on the quadrigeminal cistern, causing cerebellum compression and hydrocephalus. The clinical conditions of the child progressively worsened and blood tests revealed a severe deficit of FVIII levels. The radiological images were re-evaluated; vascular anomalies were excluded and the diagnosis of haematoma was made. Family history was negative for coagulation disorders. Molecular studies revealed a rearrangement of the FVIII gene involving intron 22. The haemophilia A diagnosis can be challenging. Lack of family history, difficulties in detecting haematomas by imaging techniques, female sex and neonatal age represent misleading factors that can delay the diagnosis.