Flowcytometric detection of PNH defect in Indian patients with aplastic anemia and myelodysplastic syndromes

Value of CD16/CD66b/CD45 in comparison to CD55/CD59/CD45 in diagnosis of paroxysmal nocturnal haemoglobinuria: An Indian experience

Background & objectives:

Diagnosis of paroxysmal nocturnal haemoglobinuria (PNH), a rare haematopoietic stem cell disorder, is challenging in patients with bone marrow failure (BMF) syndrome like aplastic anaemia (AA). This study was conducted with the aim to test the efficacy of the newly recommended markers viz. anti-CD16 and CD66b antibody over the existing anti-CD55 and CD59 antibody for PNH diagnosis in India.

Methods:

This study was conducted on 193 suspected cases of PNH by flow cytometry using lyse wash technique to stain the granulocytes with CD16/CD66b and CD55/CD59.

Results:

Of the 193 suspected cases, 62 patients showed the presence of PNH clone. Forty six patients were detected by CD55/CD59/CD45, whereas 61 were detected by CD16/CD66b/CD45. CD16/CD66b detected 16 (25.8%) additional patients over CD55/CD59 (P<0.05) and was more sensitive in detecting the PNH clone with higher negative predictive value. Most of the patients (11/16) who were picked up by CD16/CD66b were of AA who had small clone sizes. Further, the PNH clones were more discreetly identified in CD16/CD66b plots than by CD55/CD59. Clone size assessed by CD16/CD66b which reflects the clinical severity of classical PNH (thrombosis/haemolysis), was more representative of the underlying clinical condition than CD55/59.

Interpretation & conclusions:

In our experience of 62 patients of PNH, CD16/CD66b proved to be more efficacious in detecting PNH. The new panel was especially useful in monitoring PNH associated with BMF which had small clone sizes.

Frequency of Paroxysmal Nocturnal Hemoglobinuria Clones by Multiparametric Flow Cytometry in Pediatric Aplastic Anemia Patients of Indian Ethnic Origin

BACKGROUND

The literature on paroxysmal nocturnal hemoglobinuria (PNH) in aplastic anemia (AA) is largely focused on adults with few studies in children. Moreover, large studies are conspicuously absent from developing countries. Knowledge of the prevalence and utility of their detection is required before widespread use of PNH screening in pediatric AA in resource-limited settings.

METHODS

We performed a retrospective audit over a period of 9 years to study the prevalence of PNH clones by flow cytometry (FCM) in children ≤12 years of age presenting with AA, and analyzed their response to immunosuppressant therapy.

RESULTS

Nine (12.9%) out of 70 patients had PNH clones comprising >1% of the target cell population, including five patients (7.14%) with PNH clone size >10%. The clone size in monocytes ranged from 3.7% to 95.2% (median 21.1%) and in neutrophils from 1.6% to 87.6% (median 19.5%). Fluorescent aerolysin (FLAER)-based FCM screening significantly improved the detection of PNH clones compared to non-FLAER based screening techniques (18.4% vs. 6.25%). One child showed chronic intravascular hemolysis and another developed arterial stroke during the course of illness. None of our PNH-positive AA patients tested for chromosome breakage studies (n = 8) showed increased clastrogen-induced breakage.

CONCLUSIONS

A lower frequency but moderate/large-sized PNH clones were seen in our pediatric AA population, compared to western data. FLAER-based FCM screening significantly improved the detection of PNH clones. We recommend routine FLAER-based screening of PNH in pediatric AA patients.

Primary/de novo paroxysmal nocturnal hemoglobinuria in a child from north India: a case report with review of literature

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hematologic disorder, characterized by intravascular hemolysis, thrombosis, or bone marrow failure. It is very rare in children. The clinical manifestations are due to deficiency of a family of membrane proteins that are anchored into the cell membrane through glycosylphosphatidylinositol (GPI). Currently, flow cytometric analysis of GPI-linked proteins has replaced the traditional Ham test (acidified-serum lysis test) and sucrose lysis test, it being a quantitative and more sensitive method. The only curative treatment of the disease is stem cell transplantation. We are reporting a case of de novo pediatric PNH, presenting with hemoglobinuria and a sizeable clone of GPI-anchor deficient blood cells, along with review of reported cases of PNH in pediatric patients. PNH can occur in children and has varied clinical and hematologic presentations; the presence of PNH should be considered in every child with an acquired bone marrow failure, unexplained hemoglobinuria and/or unexpected serious thrombosis. Pediatricians should keep this disorder in mind, when patients present with above features.

Paroxysmal nocturnal hemoglobinuria in childhood and adolescence--a retrospective analysis of 18 cases

OBJECTIVE

To assess the clinical and hematological profile of PNH in children.

METHODS

Clinical and laboratory features of children with PNH diagnosed in the past six years at our centre were reviewed. Various investigations done included a complete blood count and peripheral smear examination, plasma hemoglobin, urine hemosiderin, acid ham test, sucrose lysis test, immunophenotyping of erythrocytes by sephadex column gel card and of granulocytes by flow cytometry. There were 18 children with a marked male predominance (M 14: F 4).

RESULTS

Pallor, jaundice, dark urine and bleeding manifestations were the major presenting complaints. One girl suffered an arterial stroke. All children had cytopenia in at least one cell line. Children were treated with danazol, stanazolol, prednisolone and cyclosporin A variously. Overall response rate was 61%. Children with classical PNH performed slightly better with response rates of 66% (6/9) as compared to aplastic anemia-PNH group which has a response rate of 55% (5/9). Amongst various variables only danazol correlated with better response (p=0.029).

CONCLUSION

PNH is an uncommon disease in children and should be included in the differential diagnosis of children presenting with cytopenia.