PAMI Syndrome: Two Cases of an Autoinflammatory Disease with an ALPS-Like Phenotype

PSTPIP1-associated myeloid-related proteinemia inflammatory (PAMI) syndrome: A case report and review of the literature

PSTPIP1-associated myeloid-related proteinemia inflammatory (PAMI) syndrome is a rare autoinflammatory disorder often arising in pediatric patients. We present a case of an 18-year-old female with a past medical history of growth failure, immunoglobulin A nephropathy, and inflammatory arthritis who presented to a pediatric dermatology clinic with findings of acne, psoriasiform dermatitis, and hidradenitis suppurativa, whose clinical, genetic, and laboratory findings were most consistent with PAMI syndrome. We conducted a literature review to better characterize this rare condition in the context of dermatologic findings. Recognition of the distinctive skin findings seen in PAMI syndrome can help distinguish it from other inflammatory disorders, enabling expedited diagnosis and treatment.

Revisiting double-negative T cells in autoimmune lymphoproliferative immunodeficiencies: a case series

BACKGROUND

Elevated level of double-negative T (DNT) cells is a historical hallmark of autoimmune lymphoproliferative syndrome (ALPS) diagnosis. However, the peripheral blood level of DNT cells might also be compromised in autoimmune lymphoproliferative immunodeficiencies (ALPID) other than ALPS, inattention to which would increase the delay in diagnosis of the underlying genetic defect and hinder disease-specific treatment.

MATERIALS AND METHODS

This cross-sectional study recruited patients suffering from ALPID (exclusion of ALPS) with established genetic diagnosis. Following thorough history taking, immunophenotyping for lymphocyte subsets was performed using BD FACS CaliburTM flowcytometry.

RESULTS

Fifteen non-ALPS ALPID patients (60% male and 40% female) at a median (interquartile range: IQR) age of 14.0 (7.6-21.8) years were enrolled. Parental consanguinity and family history of immunodeficiency were present in 8 (53.3%) patients. The median (IQR) age at first presentation, clinical and molecular diagnosis were 18 (4-36) months, 8.0 (4.0-17.0) years, and 9.5 (5.0-20.9) years, respectively. Molecular defects were observed in these genes: LRBA (3, 20%), CTLA-4 (2, 13.3%), BACH2 (2, 13.3%), AIRE (2, 13.3%), and FOXP3, IL2Rβ, DEF6, RASGRP1, PIK3CD, and PIK3R1 each in one patient (6.7%). The most common manifestations were infections (14, 93.3%), autoimmunity (12, 80%), and lymphoproliferation (10, 66.7%). The median (IQR) count of white blood cells (WBCs) and lymphocytes were 7160 (3690-12,600) and 3266 (2257-5370) cells/mm3, respectively. The median (IQR) absolute counts of CD3+ T lymphocytes and DNTs were 2085 (1487-4222) and 18 (11-36) cells/mm3, respectively. Low lymphocytes and low CD3+ T cells were observed in 3 (20%) patients compared to normal age ranges. Only one patient with FOXP3 mutation had DNT cells higher than the normal range for age.

CONCLUSIONS

Most non-ALPS ALPID patients manifested normal DNT cell count. For a small subgroup of patients with high DNT cells, defects in other IEI genes may explain the phenotype and should be included in the diagnostic genetic panel.

PSTPIP1-Associated Myeloid-Related Proteinemia Inflammatory (PAMI) Syndrome: A Systematic Review

PSTPIP1 (proline-serine-threonine phosphatase-interactive protein 1)-associated myeloid-related proteinemia inflammatory (PAMI) syndrome, previously known as Hyperzincemia/Hypercalprotectinemia (Hz/Hc) syndrome, is a recently described, rare auto-inflammatory disorder caused by specific deleterious variants in the PSTPIP1 gene (p.E250K and p.E257K). The disease is characterized by chronic systemic inflammation, cutaneous and osteoarticular manifestations, hepatosplenomegaly, anemia, and neutropenia. Increased blood levels of MRP 8/14 and zinc distinguish this condition from other PSTPIP1-associated inflammatory diseases (PAID). The aim of this systematic review is to provide a comprehensive overview of the disease phenotype, course, treatment, and outcome based on reported cases. This systematic review adheres to the PRISMA guidelines (2020) for reporting. A literature search was performed in Embase, Medline, and Web of Science on 13 October 2022. The quality of the case reports and case series was assessed using the JBI checklists. Out of the 43 included patients with PAMI syndrome, there were 24 females and 19 males. The median age at onset was 3.9 years. The main clinical manifestations included anemia (100%), neutropenia (98%), cutaneous manifestations (74%), osteoarticular manifestations (72%), splenomegaly (70%), growth failure (57%), fever (51%), hepatomegaly (56%), and lymphadenopathy (39%). Systemic inflammation was described in all patients. Marked elevation of zinc and MRP 8/14 blood levels were observed in all tested patients. Response to treatment varied and no consistently effective therapy was identified. The most common therapeutic options were corticosteroids (N = 30), anakinra (N = 13), cyclosporine A (N = 11), canakinumab (N = 6), and anti-TNF (N = 14). Hematopoietic stem cell transplantation has been recently reported to be successful in five patients. Our review highlights the key characteristics of PAMI syndrome and the importance of considering this disease in the differential diagnosis of patients presenting with early-onset systemic inflammation and cytopenia.

Strong inflammatory signatures in the neutrophils of PAMI syndrome

PSTPIP1 (proline-serine-threonine phosphatase-interactive protein 1)–associated myeloid-related proteinemia inflammatory (PAMI) syndrome is a rare autoinflammatory disease caused by heterozygous gain-of-function mutation in PSTPIP1. As one of the PSTPIP1-associated inflammatory diseases (PAIDs), neutropenia is a distinct manifestation to separate PAMI syndrome from other PAIDs. This study aimed to investigate the potential role of neutrophils and inflammatory signatures in the pathogenesis of PAMI. PAMI neutrophils displayed markedly increased production of interleukin-1β (IL-1β) and IL-18 by enzyme linked immunosorbent assay (ELISA) assay and intracellular cytokine staining. ASC speck formation and lactic dehydrogenase (LDH) release are also increased in patient neutrophils suggesting elevated pyrin inflammasome activation followed by upregulated cell death in PAMI neutrophils. RNA sequencing result showed strong inflammatory signals in both nuclear-factor kappa B (NF-κB) pathway and interferon (IFN) pathway in patient neutrophils. This study highlighted that elevated proinflammatory cytokines IL-1β and IL-18, increased pyrin inflammasome activation, and upregulation of NF-κB and IFN signaling pathways in neutrophils play important roles in pathogenicity of PAMI syndrome.