Screening assays for primary haemophagocytic lymphohistiocytosis in children presenting with suspected macrophage activation syndrome

BACKGROUND

Primary haemophagocytic lymphohistiocytosis (HLH) screening assays are increasingly being performed in patients presenting with macrophage activation syndrome (MAS). The objective of this study was to describe their diagnostic and prognostic relevance in children who had presented to paediatric rheumatology and had undergone investigative work up for MAS.

METHODS

Data was obtained retrospectively from an existing protein screening assay database and patient records. Assays included: intracellular expression of perforin in CD56+ Natural Killer (NK) cells; CD107a Granule Release Assay (GRA) in response to PHA in NK cells, or anti-CD3 stimulation of CD8 lymphocytes; in males Signal Lymphocyte Activating Molecule Associated Protein (SAP), and X-linked Inhibitor of Apoptosis Protein (XIAP) expression. All assays, requested by paediatric rheumatology, of children who had undergone investigative work up for MAS over a 5-year period (2007-2011) were included.

RESULTS

Twenty-one patients (15 female), median age 6.5 years (range 0.6-16) with follow-up of 16 months (range 1-51), were retrospectively identified. At presentation, 3/21 (14 %) fulfilled HLH-2004 diagnostic criteria. At least one screening test result was available for all 21 patients; 7/21 (33 %) had at least one persistent screening test abnormality. Of this group 4/7 (57 %) died or required haematopoietic stem cell transplantation (HSCT), compared to 1/14 (7 %) with no screening test abnormality (p = 0.025). 3/21 (14 %) ultimately had a diagnosis of primary HLH (two confirmed genetically; XIAP, familial HLH type 3, and one confirmed clinically). Of the six patients with abnormal GRA 5/6 had negative routine genetic results.

CONCLUSIONS

Screening for primary HLH is warranted for children whose first rheumatological presentation is with MAS, since overall 14 % had an eventual diagnosis of primary HLH. A persistently abnormal GRA in patients presenting with MAS defines a high-risk group with poor outcome (mortality or HSCT), possibly due to as yet unidentified genetic cause.

Adenosine deaminase deficient severe combined immunodeficiency presenting as atypical haemolytic uraemic syndrome

PURPOSE

Adenosine deaminase (ADA) deficiency is a systemic disorder of purine metabolism. Deficiency of the purine salvage enzyme ADA leads to the build-up of the toxic metabolites, deoxyadenosine triphosphate and deoxyadenosine. ADA is ubiquitously expressed in all tissues of the body but most profoundly affects lymphocyte development and function leading to severe combined immunodeficiency (SCID). Unlike most other forms of SCID, ADA deficiency also results in non-immunologic manifestations. Associations between ADA deficiency and sensorineural hearing loss, behavioural abnormalities, non-infectious pulmonary disease and skeletal dysplasia are all recognised, and affect the long term outcome for these patients. Identification of new non-immunological manifestations and clinical presentations of ADA deficiency is essential to allow early optimisation of supportive care.

METHODS AND RESULTS

Here we report four patients with ADA deficiency whose presenting feature was haemolytic uremic syndrome (HUS). 3 of 4 patients were diagnosed with ADA deficiency only after developing HUS, and one diagnosis was made post mortem, after a sibling was diagnosed with SCID. Shiga-toxigenic organisms were not isolated from any of the patients. 2 patients made a good recovery from their HUS with supportive treatment and initiation of PEG-ADA. Both remain well on enzyme replacement with mild or no residual renal impairment.

CONCLUSIONS

Clinicians should be aware of this previously unreported non-immunologic manifestation of ADA deficiency.