Diagnosis of XLP1

The most important step is recognising that there is a problem with the immune
system and involving the right specialists to investigate and treat further. Diagnosis depends on the recognition of suggestive clinical features, along with blood tests. There are many conditions that can cause similar symptoms and it is important that careful evaluation is performed to exclude any of these.

Blood tests are the main form of diagnosis and will be used to measure the levels
of SAP present in the blood. If SAP is found to be absent or in low level, the
presence of a gene mutation will also be checked through a blood sample.

A sample (biopsy) of bone marrow may also be taken, along with small samples
of lymph node tissue. Bone marrow is the spongy tissue inside bones and contains cells that produce white blood cells, red blood cells and platelets. Bone marrow aspiration is a procedure that involves using a syringe to aspirate (‘suck out’) liquid bone marrow, usually from the hip bone. If there are neurological symptoms, such as headache, vomiting, irritability, visual disturbances or seizures, a sample of cerebrospinal fluid may be taken by lumbar puncture.