Primary immune regulatory disorders in two children with autoimmune cytopenia (a challenge for the pediatrician): case report

¹Department of Pediatric Hematology-Oncology, CHU Hassan II, Fez, Morocco, ²Laboratory of Clinical Immunology, Infection and Autoimmunity, Faculty of Medicine and Pharmacy, Casablanca, Morocco, ³Department of Pediatric Infectious Diseases and Clinical Immunology, CHU Ibn Rochd, Casablanca, Morocco, ⁴Department of Pediatrics, CHU Hassan II, Fez, Morocco

^&Corresponding author
Zakaria Kasmi, Laboratory of Clinical Immunology, Infection and Autoimmunity, Faculty of Medicine and Pharmacy, Casablanca, Morocco

Introduction    

Inborn errors of immunity (IEI) are a heterogeneous group of genetic disorders characterized by defects in one or more components of the immune system, leading to a wide spectrum of clinical manifestations [1]. These include increased susceptibility to recurrent severe infections, allergic disease, lymphoproliferation, and immune dysregulation with a broad range of autoimmune and autoinflammatory disorders [1]. Advances in molecular immunology and next-generation sequencing have vastly expanded our understanding of IEI, with more than 500 distinct IEI now identified according to the latest International Union of Immunological Societies (IUIS) classification [2]. Among the various subgroups, primary immune regulatory disorders (PIRDs) have emerged as a distinct category of IEI, defined predominantly by profound immune dysregulation rather than by recurrent infections [3].

PIRDs result from pathogenic mutations that affect immune tolerance pathways or regulatory mechanisms controlling lymphocyte activation, apoptosis, and cytokine signaling. These defects lead to exaggerated immune responses and breakdown of self-tolerance, manifesting clinically as severe autoimmunity, lymphoproliferation, hyperinflammation, and sometimes increased susceptibility to malignancies [2,3]. Autoimmune cytopenias (AIC), including autoimmune hemolytic anemia (AIHA), immune thrombocytopenic purpura (ITP), and autoimmune neutropenia (AIN), are among the most frequent autoimmune features associated with PIRDs and can represent the initial presentation in children [3,4]. Indeed, the relative risk of developing an autoimmune cytopenia in patients with IEI is estimated to be well over 100-fold higher than in the general population [4]. Furthermore, combined autoimmune cytopenias such as AIHA with ITP (Evans syndrome) are highly suggestive of an underlying monogenic immune disorder, with one study finding identifiable monogenic causes in up to 65% of pediatric Evans syndrome cases [5]. Early recognition of these warning signs is crucial to prompt a comprehensive immunological evaluation, confirm a molecular diagnosis, and implement targeted therapies.

In this context, we report two pediatric cases that initially presented with chronic, refractory autoimmune cytopenias. Their diagnostic journey illustrates the considerable challenges clinicians face when confronted with atypical or complex immune dysregulation. Through these cases, we aim to emphasize two distinct PIRDs, autoimmune lymphoproliferative syndrome and LRBA deficiency, and underscore the importance of early genetic testing and multidisciplinary management to improve patient outcomes.

Patient and observation     

Case 1

Patient information: a 5-year-old boy, born to first-degree consanguineous parents, presented with persistent mucocutaneous pallor, cervical lymphadenopathy, and splenomegaly. These symptoms have been present since early infancy (around 15 months of age). There was no significant past medical history aside from recurrent pallor, and no known family history of similar illness.

Clinical results: on examination, the child had marked growth retardation (height and weight both at -2 SD for age) and a “tumoral” syndrome marked by massive splenomegaly extending to the right iliac fossa, along with multiple enlarged cervical and axillary lymph nodes. Cervical and abdominal ultrasonography confirmed splenomegaly (approximately 14 cm in length) and numerous intra-abdominal and retroperitoneal lymphadenopathies. A thoraco-abdomino-pelvic CT scan further demonstrated extensive supra- and infra-diaphragmatic lymphadenopathy with homogeneous splenomegaly (Figure 1). Laboratory evaluations showed a severe microcytic, hypochromic anemia with marked reticulocytosis, consistent with a regenerative process. The leukocyte counts revealed leukopenia with neutropenia and relative lymphocytosis, and the platelet count was moderately decreased. Inflammatory markers were notable for an accelerated erythrocyte sedimentation rate with normal ferritin and a negative C-reactive protein (CRP), suggesting the absence of an acute inflammatory response.

Diagnostic approach: given the prominent lymphoproliferative features (massive splenomegaly and generalized lymphadenopathy), initial investigations focused on ruling out neoplastic disorders (such as leukemias or lymphomas), storage diseases (notably Gaucher disease), and chronic infections. Comprehensive infectious disease testing was negative, including serologies for Epstein-Barr virus, cytomegalovirus, hepatitis B and C, HIV, and Leishmania, as well as tuberculosis screening with an interferon-gamma release assay. An extensive autoimmune workup showed no evidence of systemic lupus erythematosus or other connective tissue disease (antinuclear and double-stranded DNA antibodies were negative). Metabolic tests, including serum angiotensin-converting enzyme levels and beta-glucocerebrosidase activity, were within normal limits. Bone marrow aspirate and biopsy revealed reactive marrow with no malignant infiltration or hemophagocytic activity. Notably, the Coombs test was strongly positive, indicating autoimmune hemolysis and confirming autoimmune hemolytic anemia (AIHA) as the cause of the child's anemia. Despite these findings, an underlying diagnosis remained elusive through the initial workup.

Therapeutic intervention and follow-up: the patient was empirically treated with oral corticosteroids (prednisone) for six months due to the AIHA. However, there was no significant clinical improvement: pallor and cytopenias persisted, and lymphadenopathy and splenomegaly progressively worsened. The child required multiple hospitalizations for further evaluations, all of which failed to identify a cause for his immune dysregulation. A lymph node excisional biopsy was performed; histopathology showed an effaced nodal architecture with a polymorphous lymphoid population but no evidence of malignancy. Given the ongoing lymphoproliferation and refractory cytopenia, an immunological evaluation was finally undertaken during a third hospitalization. This revealed polyclonal hypergammaglobulinemia and an expansion of circulating double-negative T cells (TCRβ⁺/CD4/CD8 lymphocytes), which are suggestive of autoimmune lymphoproliferative syndrome. Serum vitamin B12 levels were markedly elevated (approximately 2500 ng/L), a known laboratory finding in ALPS. Targeted genetic testing subsequently identified a homozygous pathogenic variant in the FAS gene (NM_000043.6: c.506-1G>C), confirming the diagnosis of ALPS. Therapy was switched to the immunosuppressant mycophenolate mofetil (MMF), which resulted in a notable clinical improvement: the patient's hemoglobin stabilized, and there was a gradual reduction in lymphadenopathy and splenomegaly on follow-up.

Patient consent: written informed consent was obtained from the patient's legal guardians for publication of this case's details and accompanying images.

Case 2

Patient information: a 5-year-old girl, also born to first-degree consanguineous parents, was hospitalized for a prolonged febrile illness. She had a family history notable for an older brother who had died at 8 months of age from an undiagnosed febrile illness. There were no other known hereditary diseases in the family.

Clinical results: on initial examination, the patient exhibited marked growth failure (height and weight at approximately -3 SD for age), moderate splenomegaly, and persistent fever. Initial laboratory tests revealed bicytopenia (anemia and profound neutropenia) accompanied by a markedly elevated C-reactive protein, indicating an active inflammatory process. Other routine laboratory findings were unremarkable. Bone marrow aspirate and biopsy showed reactive changes without malignant infiltration or storage cells. Extensive infectious workup was negative, including tests for HIV, CMV, EBV, hepatitis A/B/C, and leishmaniasis. The patient was managed as a case of febrile neutropenia with broad-spectrum antibiotics and subsequently corticosteroids, given the suspicion of an immune-mediated process.

Two months after the initial presentation, she developed progressive abdominal distension with chronic, watery diarrhea and significant weight loss, occasionally accompanied by vomiting. Stool examinations were negative for infectious pathogens. Abdominal imaging (CT scan) revealed hepatomegaly, splenomegaly, and confluent coelio-mesenteric lymphadenopathy (Figure 2A). Given the combination of prolonged diarrhea, fever, and radiologic evidence of intestinal inflammation, intestinal tuberculosis was suspected, and empiric anti-tuberculous therapy was initiated. However, this treatment was complicated by drug-induced hepatitis, and no improvement in the gastrointestinal symptoms was observed after several weeks. Anti-tuberculous therapy was eventually discontinued due to lack of efficacy. Two months later, the patient developed arthritis of the left hip. Synovial fluid analysis was sterile, and no etiologic agent was identified. Radiographs and CT imaging of the bones revealed multiple metaphyseal osteolytic lesions in the pelvis and distal femurs (Figure 2B). Around the same time, she experienced recurrent episodes of hypocalcemia due to malabsorption and vitamin D deficiency, requiring repeated hospitalizations for electrolyte correction and nutritional support.

Diagnostic approach: the combination of refractory cytopenia (neutropenia and anemia), chronic gastrointestinal symptoms, lymphoproliferation (hepatosplenomegaly and lymphadenopathy), and autoimmune complications (arthritis, osteolytic lesions) raised suspicion for an underlying immune dysregulatory disorder. A broad immunological workup was undertaken. Flow cytometry did not show features of ALPS (no expansion of double-negative T cells in this patient). Given the multi-system involvement, a primary immune regulatory disorder was considered. Genetic testing for monogenic causes of immune dysregulation was performed. At the age of 4 (nearly a year after her initial presentation), the patient was diagnosed with LRBA deficiency. A biallelic loss-of-function mutation in the LRBA gene (LRBA: c.5060_5067del) was identified, confirming the molecular diagnosis.

Therapeutic intervention and follow-up: the patient's initial treatment after the diagnosis of LRBA deficiency included MMF (to target autoimmunity) combined with low-dose corticosteroids and monthly intravenous immunoglobulin infusions. Despite this regimen, her clinical condition did not improve substantially. At the age of 4, therapy with abatacept (a CTLA-4 fusion protein) was initiated. This biological therapy led to remarkable improvement: her blood count normalized, the diarrhea resolved, and the arthritis and bone lesions showed healing. Unfortunately, five months after starting abatacept, the patient developed interstitial lung disease (ILD) as a complication of her underlying condition, presenting with cough, chest pain, and progressive respiratory distress. She also developed type 1 diabetes mellitus, which presented acutely with diabetic ketoacidosis, reflecting ongoing immune-mediated damage (autoimmune endocrinopathy). Despite these complications, the patient's condition stabilized with appropriate management of ILD and diabetes, and she remains under close follow-up.

Patient consent: written informed consent for participation in this case report and for publication of the clinical details and images was obtained from the patient's parents.

Discussion     

IEIs can manifest not only with recurrent or severe infections, but also with profound immune dysregulation [1,3]. According to the IUIS classification, diseases of immune dysregulation represent a distinct category of IEI (sometimes termed the fourth subgroup) [2]. In contrast to “classical” primary immunodeficiencies that present mainly with infections, PIRDs are characterized predominantly by immune-mediated pathology: severe autoimmunity, autoinflammation, lymphoproliferation, malignancy, and atopy can all be prominent features [1,3]. A prototypical PIRD is IPEX syndrome (immune dysregulation, polyendocrinopathy, enteropathy, X-linked), but the spectrum of genetic defects in PIRDs has expanded rapidly in recent years [3]. These disorders are heterogeneous, and several pathogenic mechanisms can lead to similar clinical phenotypes. For example, “Tregopathies” are a group of PIRDs caused by dysfunction of regulatory T cells and include conditions such as IPEX syndrome, CTLA-4 haploinsufficiency, and LRBA deficiency [3]. Other PIRDs involve unchecked innate immune activation (as in certain autoinflammatory syndromes) or failures of central tolerance (as in APECED), while some result from defective lymphocyte apoptosis leading to accumulation of autoreactive lymphocytes, as seen in autoimmune lymphoproliferative syndrome (ALPS) [3]. The broad and overlapping presentations of PIRDs often result in patients being initially evaluated by general pediatricians or subspecialists (e.g., hematologists) rather than immunologists. This can delay the consideration of an underlying immune defect. Autoimmune cytopenias are now recognized as a common manifestation of many IEIs [4]. These cytopenias may be the first clinical sign of an IEI (preceding any severe infections) or may arise during the course of a known immunodeficiency. In either scenario, refractory or combined autoimmune cytopenias in a child should prompt an evaluation for an underlying monogenic immune disorder. The cases presented here illustrate this point: each child's chronic cytopenia was an early clue to an underlying PIRD, although the diagnoses (ALPS in Case 1 and LRBA deficiency in Case 2) were significantly delayed.

Autoimmune lymphoproliferative syndrome is a quintessential disorder of impaired lymphocyte apoptosis. Most cases are due to mutations in FAS or related genes, leading to defective FAS-mediated apoptosis of lymphocytes [6]. The resulting accumulation of autoreactive T cells (particularly the so-called double-negative T cells that lack both CD4 and CD8) drives non-malignant lymphoproliferation and autoimmunity in ALPS [6]. Clinically, ALPS typically presents in early childhood with chronic nontender lymphadenopathy, hepatosplenomegaly, and autoimmune cytopenias (most commonly AIHA or ITP) [6]. In one series of ALPS patients, the majority had detectable autoantibodies; AIHA occurred in a substantial subset and ITP in nearly half of the cases [6]. In our first patient, severe Coombs-positive AIHA developed in infancy and was refractory to steroids, consistent with ALPS. His persistent lymphoproliferation (massive spleen and lymph nodes) and elevated vitamin B12 level were additional clues to the diagnosis. Genetic confirmation came through identifying a homozygous FAS splice-site mutation. Institution of second-line immunosuppressive therapy (MMF) led to disease control. This case underscores that ALPS should be suspected in young patients with unexplained chronic lymphadenopathy, splenomegaly, and Coombs-positive autoimmune cytopenia.

The second case highlights LRBA deficiency, a complex PIRD that exemplifies a “Tregopathy”. LRBA deficiency was first described in 2012 and is caused by biallelic mutations in the LRBA gene, leading to loss of the LRBA protein [7]. Clinically, LRBA deficiency has a broad spectrum of manifestations, including early-onset autoimmunity (often affecting blood cells, gut, and endocrine organs), chronic diarrhea (immune-mediated enteropathy), recurrent infections (due to concomitant hypogammaglobulinemia), lymphoproliferation (organomegaly, lymphadenopathy), and growth failure [7]. Our patient manifested many classic features: she had refractory cytopenias, chronic diarrhea, arthritis, bronchopulmonary disease, and autoimmune diabetes. The pathophysiology of LRBA deficiency involves impaired regulation of CTLA-4, a critical inhibitory receptor on T cells. Normally, LRBA protein helps recycle and maintain CTLA-4; in its absence, CTLA-4 is rapidly degraded, leading to excessive T-cell activation [7]. This mechanism provided the rationale for treating our patient with abatacept (a CTLA-4-Ig fusion protein). Notably, she showed significant improvement on abatacept, consistent with reports that CTLA-4 augmentation therapy can ameliorate autoimmunity in LRBA deficiency [7]. Nevertheless, her disease course was complicated by progressive lung disease and type 1 diabetes, reflecting the ongoing challenge of managing multi-system autoimmunity even after diagnosis.

Together, these two cases illustrate the importance of considering an underlying primary immunoregulatory disorder in children with difficult-to-treat autoimmune cytopenias. Prompt genetic diagnosis can directly inform therapy, for instance, encouraging the early use of steroid-sparing agents like MMF, sirolimus, or targeted biologics (such as abatacept) in ALPS or LRBA deficiency. Multidisciplinary care is often required, as patients may have complex needs involving hematology, immunology, gastroenterology, and other specialties. Ultimately, heightened awareness of the “red flags” of immune dysregulation (refractory cytopenias, atypical autoimmunity, lymphoproliferation) can facilitate earlier diagnosis of PIRDs and improve patient outcomes [8].

Ethics approval and consent to participate: the study was conducted following the ethical guidelines and regulations of Hassan II University Hospital Center of Fez. Ethical approval was obtained from the “Hassan II University Hospital Center Ethics Committee” for the broader project on Autoimmune Cytopenia in Morocco, under which this case report falls. Informed consent was obtained from the patients' legal guardians, ensuring that they were fully aware of the nature and purpose of the research.

Consent for publication: the patients' parents provided informed consent regarding publishing the data and photographs.

Availability of data and materials: all data generated or analyzed during this study are included in this published article. (No additional datasets were generated or analyzed).

Conclusion     

Primary immune regulatory disorders constitute a heterogeneous group of IEI characterized by a tight link between immune dysregulation, loss of tolerance, and autoimmunity (including cytopenias). These cases demonstrate that refractory or atypical autoimmune cytopenias in children may be the presenting sign of an underlying monogenic disorder. Early recognition and genetic diagnosis of such conditions are critical to guide targeted therapeutic management and improve prognosis.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Mohamed Hbibi and Zakaria Kasmi wrote the main manuscript. Mohamed Hbibi, Fatima Ailal, Mounia Lakhdar Idrissi, Moustapha Hida, and Ahmed Aziz Bousfiha gave academic feedback, contributed to the patient's clinical management, and revised and corrected the manuscript. All authors have reviewed the final manuscript and agreed to be accountable for the work. All authors read and approved the final version of this manuscript.

Figures     

Figure 1: contrast-enhanced cervico-thoraco-abdomino-pelvic CT scan showing multiple bilateral cervical, mediastinal, axillary, and coelio-mesenteric lymphadenopathies associated with marked splenomegaly
Figure 2: A) abdominal CT scan showing marked splenomegaly (blue arrow), hepatomegaly (red arrow), and confluent coelio-mesenteric lymphadenopathy (red circle); B) multiple metaphyseal-diaphyseal osteolytic lesions involving the femur, ribs, and right iliac bone, with cortical bone lysis in some areas

References