Table I. Typical characteristics of classical WAS and XLT patients.

	Classical WAS	XLT
Clinical features
Thrombocytopenia	Yes	Yes
Eczema	Moderate/severe	None/mild
Infections	Yes	None/mild
Autoimmunity	Yes	No*
Malignancy	Yes	No
Typical WASp expression	Absent/low levels	Low/normal levels
Typical WAS mutation	Deletions/insertions/early stop codon/splice site	Missense/splice site

A clinical scoring system is often used to aid classification of WAS patients, with one point assigned for each clinical feature (Zhu et al, 1995; Ochs et al, 2009). A score of ≥3, suggestive of a more severe phenotype, typically correlates with a diagnosis of classical WAS.

WAS, Wiskott-Aldrich syndrome; WASp, WAS protein; XLT, X-linked thrombocytopenia.

^*Some centres will consider a diagnosis of XLT with autoimmunity where this develops at a later stage, in the context of a mutation known to be associated with XLT and without other clinical features of classical WAS, such as severe/recurrent infections.