Jussara Soares Fontes^1,2, Thalles Trindade de Abreu², Isabela Gontijo e Couto², Larissa Siqueira Campos¹, Maria Goretti Moreira Guimarães Penido^3,4*

¹Federal University of São João Del Rei - Faculty of Medicine of Dona Lidu Campus, Divinópolis, Minas Gerais, Brazil

²Pediatric Nephrology Unit - Nephrology Center of Complexo de Saúde São João de Deus, Divinópolis, Minas Gerais, Brazil

³Pediatric Nephrology Unit - Nephrology Center of Santa Casa de Belo Horizonte, Belo Horizonte, Minas Gerais, Brazil

⁴Federal University of Minas Gerais - Faculty of Medicine - Department of Pediatrics - Pediatric Nephrology Unit, Belo Horizonte, Minas Gerais, Brazil

*Corresponding Author: Maria Goretti Moreira Guimarães Penido, Pediatric Nephrology Unit - Nephrology Center of Santa Casa de Belo Horizonte, Belo Horizonte, Minas Gerais, Brazil. Federal University of Minas Gerais - Faculty of Medicine - Department of Pediatrics - Pediatric Nephrology Unit, Belo Horizonte, Minas Gerais, Brazil. ORCID: 0000-0002-1534-3861

Abstract
Background: Anti-glomerular basement membrane (anti-GBM) disease is a rare entity in the pediatric population characterized by rapidly progressive glomerulonephritis (RPGN), often without pulmonary involvement. It is a double seropositive disease, consisting of anti-GBM antibody plus anti-neutrophil cytoplasmic antibodies. The diagnosis is based on an RPGN clinical presentation combined with serological detection of circulating antibodies and/or direct immunofluorescence of renal biopsy. The recommended treatment is plasmapheresis as soon as possible. Although it has been described as rare in children, its possibility must be considered in the differential diagnosis of acute renal failure and glomerulonephritis.

Case–Diagnosis/Treatment: We report the case of a 13-year-old male patient who presented o the emergency department with fever, fatigue, inappetence, and vomiting. He reported having dark urine with normal urine output. On physical exam, he was pale-looking with tachycardia, tachypnea, and a systolic heart murmur on auscultation. The lungs were normal on auscultation and there were no edema or skin spots. There was significant anemia, Acute kidney injury (AKI), hyperkalemia, depressed iron stores. The assessment of serology showed C-ANCA reagent, P-ANCA not reagent. Hemolysis tests, serum complement, and Anti-GBM antibody were normal. Glomerular hematuria and nephrotic range proteinuria were present. COVID-19 test negative. The diagnosis was confirmed only after the kidney biopsy.

After excluding infections, we started methylprednisolone followed by prednisone, cyclophosphamide orally, and plasmapheresis was initiated. Unfortunately, the patient did not recover renal function and remains on a chronic hemodialysis program.

Conclusion: We do believe that any case of anti-GBM should be described to better understand this rare pediatric disease.

Keywords: Children, anti-GBM, end-stage renal disease, Goodpasture’s disease

Introduction
Anti-glomerular basement membrane (anti-GBM) disease is uncommon in children and is characterized by rapidly progressive glomerulonephritis (RPGN) or pulmonary-renal syndrome with alveolar hemorrhage, known as Goodpasture syndrome [1-3]. It is caused by autoantibodies (classically type G immunoglobulin) directed against the α3 subunit of type IV collagen [2-5]. The autoantibodies target an antigen expressed in the basement membranes of these organs, however, the events that initiate and induce the autoimmune response are not fully understood [2-5]. It is believed that environmental factors, including infection, cigarette smoking, and others can trigger the disease in genetically susceptible individuals [2,6].

Anti-GBM disease occurs in 0.5–1 case per million/year in adult patients [3]. Most affected patients are adolescents and adults of all ages, and the male-to-female ratio varies from 1:1 to 9:1 [7]. About one-quarter of patients will also have antineutrophil cytoplasmic antibodies (ANCA) associated with vasculitis and other kidney diseases such as membranous nephropathy [8,9]. The coexistence of circulating antibodies against GBM and ANCAs (double or dual positivity) in children is extremely rare with only seven patients reported to date [9]. In addition, atypical presentations of anti-GBM disease are increasingly reported [3,10].

On physical examination he had sinus tachycardia (110/min), tachypnea, a systolic heart murmur (grade 2/6) pale, clear lungs to auscultation bilaterally, no edema or skin spots. Body weight 40kg, body height 161cm, BP 140/90mmHg. Laboratory tests showed significant anemia (hemoglobin 3.4g/dL, hematocrit 11.2 %), no changes in the white series or platelets (leukocytes 6,400mm³, platelets 416,000mm³); renal dysfunction (creatinine 5.7mg/dL, urea 159mg/dL, eFGR 11,7 ml/min/1,73m² body surface), hyperkalemia (potassium 6.4mg/dL), negative hemolysis tests (negative direct coombs, normal haptoglobulin, reticulocytes and bilirubin), depressed iron stores (serum iron 11mg/dL, ferritin 95.5mg/dL, total iron-binding capacity 217, free iron-binding capacity 205, transferrin saturation index 5 %), hyperphosphatemia (6.5mg/dL), metabolic acidosis (venous blood gases pH 7.36, bicarbonate 19.3), serum albumin 3.0g/dL, total cholesterol 112mg/dL, triglycerides 41mg/dL, normal vitamin B12. The assessment of serology showed C-ANCA reagent 1:80, P-ANCA not reagent. Serum complement (C3- 136mg/dL, C4-32mg/dL, CH50-156U/L), FAN, Anti-GBM antibody, rheumatoid factor < 8, protein electrophoresis and viral serology were normal or negative (non-reactive HBsAg, Anti-HBs 14.52; non- reactive HCV). Leishmaniasis negative, Schistosomiasis non- reactive, CMV IgG 71 (+) IgM 0.19 (-), Toxoplasmosis IgG 0.20 (-) IgM 0.13 (-), Epstein Baar IgM 0.11 (-), IgG 46.72 (+), IgE alpha lactalbumin < 0.1, normal hemoglobin electrophoresis. Urine examination showed glomerular hematuria and nephrotic proteinuria (80 RBC/hpf, casts hyaline and granular casts, rare blood casts, codocytes, acanthocytes, spot urine protein to creatinine ratio 2.8). (Table 1 and 2).

Table 1: Laboratory data of the blood samples

NR: non-reactive, GFR: Glomerular filtration rate, ANCA: Antineutrophil Cytoplasmic Antibodies, ANA: Anti-nuclear antibodies, Anti-GBM: Anti-glomerular basement membrane, CMV: Cytomegalovirus.

Table 2: Laboratory data of the urine samples

RBC: red blood cells, P/C ratio: Spot urine protein to creatinine ratio.

The patient had a negative test for COVID-19 and he denied gastrointestinal bleeding, hemoptysis, or recent skin and throat infections. He received several red blood cell transfusions due to constant drops in hemoglobin, intravenous hydrocortisone and there was clinical control of hyperkalemia and acidosis.

Renal ultrasound showed kidneys in the right place with preserved dimensions, parenchyma with normal thickness, and diffusely increased echogenicity. Echocardiogram with preserved biventricular systolic function (LV ejection fraction 68%-Simpson). Negative myelogram for leishmaniasis, hemophagocytic syndromes, or other hematologic malignancies. Bone marrow with hyperplasia of the erythrocyte series without maturation of erythroid precursors. Kidney biopsy confirmed rapidly progressive crescentic glomerulonephritis in a proliferative/sclerosing phase related to the anti-GBM disease.

After excluding infections, we started immunosuppression with methylprednisolone 1.0g intravenously for 3 days, followed by prednisone 40mg/day and cyclophosphamide 50mg/day orally. Plasmapheresis was initiated (6 sessions) and corticosteroid therapy was maintained. Unfortunately, the patient did not recover renal function and required dialysis therapy.

Discussion
Few pediatric cases of the anti-GBM disease are reported. According to the literature, the majority of pediatric cases present as an RPGN. However, some cases can present with pulmonary manifestations called Goodpasture syndrome [2,3,9,10]. Here we described the case of a 13-year-old boy with the diagnosis of anti-GBM disease based on kidney biopsy and on the clinical presentation of RPGN, without pulmonary involvement. The initial signs and symptoms in our patient were fever, fatigue, inappetence, and vomiting, quite similar to those described by Bogdanović et al. [9]. According to McAdoo et al., 80 %–90 % of patients will present features of RPGN, 40 %-60 % will also have lung hemorrhage, and a small minority may present with isolated pulmonary disease [2]. It has been recognized as an atypical presentation of anti-GBM disease, often with less renal impairment, although it is unclear whether these represent distinct clinical subphenotypes or a spectrum of disease severity [2]. Studies on the adult populations with anti-GBM reported equal sex prevalence, however, it is not defined in the pediatric group [3].

Our patient had hematuria, nephrotic range proteinuria, severe anemia (hemoglobin=3.4g/dL) with decreased iron stores, AKI (creatinine=5.7mg/dL) with hyperkalemia, and hyperphosphatemia, in need of dialysis treatment. Initially, he received several red blood cell transfusions, intravenous hydrocortisone, and furosemide. The biopsy was performed with a sample of 29 glomeruli: four with active cellular crescents, two with fibro cellular crescents, 21 (72 %) with fibrous crescents, and mild/moderate fibrosis (30/40 %). Immunofluorescence reveals strong linear pattern positivity for IgG (+++/3+) in capillary loops along the basal membrane. Hematuria, nephrotic proteinuria, renal dysfunction, and its repercussion characterize an RPGN requiring kidney biopsy. Williamson et al. reported four pediatric anti-GBM cases and all had serum creatinine > 5.7mg/dL and glomerular crescents >85 % in most of them [6]. Dorval et al. identified in the literature 27 pediatric cases of anti-GBM and at diagnosis, the mean serum creatinine was 6.26±4mg/dL (n=25), and 15 children were dialyzed. Five patients died within the first two months (survival rate=81.5 %), 12 (44.5 %) had an independent renal function after a mean follow-up of two years, among dialyzed patients only three recovered renal function, and four (14.8 %) patients underwent kidney transplantation [3]. The authors also related that serum creatinine > 5.7mg/dL at diagnosis and crescentic glomeruli > 85 % are poor prognosis indicators in children [3]. However, Nagano et al. observed the anti-GBM disease in an 8-year-old girl with normal renal function (creatinine=0.4mg/dL) who had participated in a school urine screening program. The renal biopsy with 12 glomeruli showed no crescent formation. The diagnosis was confirmed with positive and high anti-GBM antibodies [15].

Williamson et al. described an 8-year-old female patient with no demonstrable circulating anti-GBM antibodies, despite prominent linear IgG staining in the glomerular and alveolar basement membrane, in IF [6]. About 2–3 % of patients with the anti-GBM disease may have circulating antibody levels that are undetectable by standard assays, but detectable by a specialized biosensor [6]. In these cases, the diagnosis could be made based on biopsy findings. Exactly as mentioned in the case above, the assessment of the anti-GBM antibody in our patient resulted in negative and the IF revealed strong linear pattern positivity for IgG in capillary loops along the basal membrane (Figure 1).

A pathogenic role for anti-GBM antibodies is supported by clinical observations and antibody titer, subclass, and avidity for the basement membrane have been correlated with disease outcomes [2]. It is known that plasma exchange is associated with better outcomes. The immunosuppression in our patient was done with intravenous methylprednisolone, followed by prednisone and cyclophosphamide orally. Concomitantly, plasmapheresis was initiated. This treatment is in accordance with the 2012 Kidney Disease Improving Global Outcomes guidelines recommendations [5]. The treatment for anti-GBM in the pediatric population is extrapolated from adult guidelines. Without the promptness of immunosuppressive therapy, the outcome is poor and natural evolution leads to ESKD and/or death [3,6,10,15].

In conclusion, we described a case of a young adolescent with an acute and poor outcome in which the anti-GBM antibodies were negative. The diagnosis was confirmed only after the kidney biopsy, although the clinical onset was an RPGN. He was treated promptly according to recommended guidelines. However, he did not regain his renal function completely and required chronic hemodialysis. We do believe that any case of anti-GBM should be described in order to better understand this rare disease.

Figure 1: Kidney biopsy. A) Jone´s stain (40X) Glomeruli injured showing rupture of the glomerular basement membrane (GBM) and proliferation of the Bowman´s capsular parietal cells with fibrocelullar crescents. B) PAS stain (40X) presenting a glomeruli tuffs evolved by fibrous crescent. C) H&E (40X) Several tubules with red cells casts. D) Immunofluorescence (40X Leica 2500 Fluorescent Microscopy 100Watts Mercury Lamp) Linear IgG stain along the GBM.
Source: Authors' personal archive.

Statements and Declarations: The authors declare no conflicts of interest between the investigators and the patients, and other institutions. 

Funding: None. 

Indication of authors' contribution:
Jussara Soares Fontes, Thalles Trindade de Abreu, Larissa Siqueira Campos, Isabela Gontijo e Couto and Maria Goretti Moreira Guimarães Penido were responsible for the research idea, study design, data acquisition, supervision or mentorship and article writing.

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