ABSTRACTS – ORAL PRESENTATIONS - AMCA, spol. s r.o.

P59. EARLY DIAGNOSTICS OF CARTILAGE-HAIR HYPOPLASIA AS A CAUSE OF SEVERE
COMBINED IMMUNODEFICIENCY (SCID) USING FLOW CYTOMETRY AND TREC/KREC
ANALYSIS
Kotrová Michaela 1 , Formánková Renata 1 , Mejstříková Ester 1 , Froňková Eva 1 , Říha Petr 1 ,
Svatoň Michael 1 , Baxová Alice 2 , Šedivá Anna 3 , Sedláček Petr 1 , Starý Jan 1
1
Department of Paediatric Haematology and Oncology, 2 nd Faculty of Medicine, Charles
University in Prague and Motol University Hospital michaela.kotrova@lfmotol.cuni.cz
2
Institute of Biology and Department of Medical Genetics 1 st Faculty of Medicine,
Charles University, Prague and General Teaching Hospital
3
Department of Immunology, 2 nd Faculty of Medicine, Charles University in Prague
and Motol University Hospital
Cartilage-hair hypoplasia (CHH), also known as metaphyseal chondrodysplasia, is a rare
autosomal recessive genetic disorder caused by mutations of the RMRP gene, encoding
non-protein RNA Component of Mitochondrial RNA Processing Endoribonuclease.
Mutations in this area can lead to a wide spectrum of signs and symptoms including
different degrees of short stature, hair hypoplasia, defective erythrogenesis, and
immunodeficiency. The immunodeficiency in CHH can present as isolated T-cell or B-cell
immunodeficiency, or combined T-cell and B-cell immunodeficiency. In CHH patients,
allogeneic hematopoietic stem cell transplantation (HSCT) can correct immune deficiency
and anemia but has no effect on skeletal changes.
A 2.5 months girl presented with systemic cytomegalovirus (CMV) disease, CMV
interstitial pneumonia and rotaviral enteritis. Flow cytometry evaluation of peripheral
blood revealed 67% of granulocytes, 6.2% of lymfocytes and 23% of monocytes according
to CD45+14++. CD19+ B lymphocytes prevailed, the T lymphocytes were in minority
(4.6%) and only CD3+4+ and TCR gamma/delta cells were present. Within CD3+4+cells,
98.2% of cells were CD45RO positive, suggesting maternofetal engraftment or oligoclonal
expansion of residual T cells. B cell compartment consisted mostly of IgD+CD27neg naïve
B cells (97%), IgMnegIgDnegCD27pos class switched memory B cells and plasmablasts
were almost missing (0.18%). The diagnosis of SCID was subsequently confirmed by
recombination circle quantitative PCR analysis aiming at detection of newly derived T
(„TREC“) and B („KREC“) cells. TRECs were not present in the peripheral blood, while
KREC levels did not differ from those in healthy newborns, indicating complete early
block in alpha/beta T-cell development and normal development of B lymphocytes until
the stage of class switching. The patient has successfully undergone HSCT at the age of
three months with unrelated matched cord blood.
The exome sequencing was performed with the aim to find underlying mutation after the
exclusion of IL7R defect. However, neither any mutation in ~20 known genes associated
with T-B+ SCID, nor any new, previously undescribed mutation was found. Skeletal
dysplasia was detected in the patient by ultrasound already in the 36th gestational
week and diagnosis of CHH was suggested by clinical genetician at the age of 5 months.
As non-protein coding gene, RMRP was not covered sufficiently in exome sequencing
library (Nimblegen SeqCap EZ Human Exome Library v2.0). We performed a molecular
158 Analytical Cytometry VII