Management of patients with severe Epstein syndrome: Review of four patients who received living‐donor renal transplantation

Kidney pathological findings of MYH9-related disease: a cross-sectional nationwide survey in Japan

BACKGROUND

MYH9-related disease (MYH9-RD) is characterized by macrothrombocytopenia, hearing loss, and progressive kidney dysfunction. Due to thrombocytopenia, kidney biopsy is seldom performed, and pathological findings remain unclear. Although case reports have described focal segmental glomerulosclerosis (FSGS) and glomerular basement membrane (GBM) abnormalities like Alport syndrome, no cross-sectional studies of MYH9-RD have been performed. This study aimed to clarify kidney pathological findings through a nationwide survey.

METHODS

We conducted a nationwide survey of MYH9-RD patients and collected tissues from kidney biopsies, along with immunofluorescence and electron microscopy images. Multiple pathologists examined all samples.

RESULTS

Nine kidney biopsy samples were included. Mesangial matrix expansion was observed in all samples (100%), while FSGS was observed in two (22%). Segmental foot process effacement was observed in all samples (100%), with irregularly aggregated podocyte dense material in seven (78%). Immunofluorescence analysis revealed that three samples (33%) had immunoglobulin and/or complement deposition: the types of depositions varied among patients. Electron dense deposits (EDD) were found in five samples (56%). GBM abnormalities - thinning, irregular thickening, and splitting of the lamina densa - were observed in five samples (56%), but no basket-weave appearance was noted. Endothelial cell swelling was found in seven samples (78%).

CONCLUSIONS

Mesangial expansion and segmental foot process effacement were commonly observed in MYH9-RD patients. Additional findings included immunoglobulin and complement deposition with EDD, and GBM abnormalities. Although patients may have had relatively severe disease, which limits generalizability, these results provide valuable insights into the disease mechanisms and potential therapeutic targets of MYH9-RD.

Novel variant in MYH9 in a child with proteinuria and thrombocytopenia: a case report and literature review

There is a lack of awareness of the diagnosis and treatment of MYH9-related disorder (MYH9-RD), which is an autosomal dominant disease with heterogeneous clinical manifestations. We summarized the clinical phenotype and reported a novel variant in MYH9 in a child with focal segmental glomerulosclerosis (FSGS) and reviewed the relevant literature to better understand MYH9-RD. Unlike previous cases, this patient exhibited IgA deposition in the mesangial region, suggesting need for further investigation into prognostic and therapeutic significance of this finding. To reduce the risk of MYH9-RD misdiagnosis, we recommend assessing mean platelet diameter and granulocyte inclusions in patients with unexplained proteinuria and refractory thrombocytopenia.

MYH9-related disease with a normal platelet count

MYH9-related disease (MYH9-RD) is characterized by congenital macrothrombocytopenia, progressive kidney failure, and sensorineural hearing loss. We describe a patient with MYH9-RD and a normal platelet count. A 13-year-old boy with a normal platelet count presented with proteinuria and hematuria and underwent a kidney biopsy. Light microscopy showed mild mesangial matrix expansion. Electron microscopy showed thinning of the glomerular basement membrane and splitting of the lamina densa. A tentative diagnosis of Alport syndrome was made. Unexpectedly, genetic analysis revealed a de novo MYH9 gene variant (p.Gln1068_Leu1074dup). A peripheral blood smear examination showed giant platelets and leukocyte inclusion bodies, confirming a diagnosis of MYH9-RD. In summary, we described a patient with MYH9-RD without thrombocytopenia who showed glomerular basement membrane abnormalities similar to Alport syndrome. Peripheral blood smear examinations may be helpful for an appropriate diagnosis of MYH9-RD, even in patients with proteinuria and a normal platelet count.

Clinical and genetic characteristics of 40 patients with nonmuscle myosin heavy chain 9-related disease (MYH9-RD) misdiagnosed as immune thrombocytopenia: a retrospective analysis in China

BACKGROUND

Myosin heavy chain 9-related diseases (MYH9-RDs) are rare autosomal dominant platelet disorders characterized by macrothrombocytopenia and leukocyte inclusion bodies. They can manifest with nonhematological complications, including deafness, nephropathy, or cataracts. Due to its rarity and its similar clinical presentation with immune thrombocytopenia (ITP), MYH9-RD is often misdiagnosed as ITP, leading to inappropriate treatment and delayed management of complications.

OBJECTIVES

This study aimed to evaluate clinical, therapeutic, and genetic aspects of patients with MYH9-RD misdiagnosed with ITP, comparing differences between Chinese pediatric and adult cases of this condition.

METHODS

This multicenter retrospective study included data obtained from Chinese patients diagnosed with MYH9-RD between January 2014 and December 2023 at 5 centers.

RESULTS

Adults exhibited significantly longer median misdiagnosis (9 years vs 0.2 years, P < .001) and treatment durations (1.5 years vs 0.1 years, P < .001) than children. Nonhematological manifestations were exclusive to adults (10/21). All patients received inappropriate ITP treatments, with adults receiving more different treatments. Genetic analysis revealed 21 spontaneous mutations (52.5%), 12 familial mutations, and 7 mutations with unknown inheritance patterns. Two novel mutations (p.G1517V and p.K1674Q) were identified. Patients with the p.R702C mutation demonstrated early-stage kidney injury and hearing loss.

CONCLUSION

Adult patients with MYH9-RD have greater risk of misdiagnosis, prolonged inappropriate treatment, and nonhematological complications than pediatric patients. Enhanced awareness, consideration of mean platelet volume, family history, and genetic screening are crucial for accurate MYH9-RD diagnosis and management. The incidence of spontaneous mutations and identified genotype-phenotype correlations warrant further investigation in the Chinese population.

MYH9-related disorder with sole presentation of end-stage kidney disease and long-term, recurrence-free living after living donor renal transplantation: a case report

MYH9-related disorders are a group of autosomal dominant disorders caused by mutations in MYH9, and are characterized by thrombocytopenia, sensorineural hearing loss, cataracts, and renal failure. Here, we report a case of chronic renal failure due to MYH9-related disorder with renal symptoms in a patient who underwent living-donor renal transplantation. The patient was diagnosed with proteinuria during a health checkup at the age of 12 years. Her renal function gradually deteriorated, and hemodialysis was initiated at 34 years of age. No definitive diagnosis of renal disease was made through renal biopsy. At the age of 35, she underwent living-donor renal transplantation from her mother as the donor. Six years after transplantation, her renal function remained stable, and no evidence of recurrent nephritis was found during renal biopsies. The family history revealed that her father, uncle, and younger brother had end-stage kidney disease. Genetic testing revealed a mutation (p.E1653D) related to the MYH9 gene. As her father had a history of renal biopsy and was diagnosed with focal segmental glomerulosclerosis (FSGS), we diagnosed chronic renal failure due to FSGS associated with MYH9 disorder. There were no findings suggestive of hearing loss, cataracts, or thrombocytopenia in the recipient or their family members with renal failure, and no symptoms other than renal failure were noted.

A nationwide survey of MYH9-related disease in Japan

BACKGROUND

MYH9-related disease (MYH9-RD) is characterized by congenital macrothrombocytopenia, Döhle body-like granulocyte inclusions, and nephropathy, which may progress to end-stage kidney disease (ESKD). However, information on the effects of renin-angiotensin system (RAS) inhibitors on kidney survival is currently lacking and the outcomes of kidney replacement therapy (KRT) in MYH9-RD are largely unknown.

METHODS

We conducted a cross-sectional nationwide survey by sending questionnaires to 145 institutions in Japan and analyzed data for 49 patients.

RESULTS

The median patient age was 27 years. Genetic analysis was performed in 37 (76%) patients. Twenty-four patients (65%) had MYH9 variants affecting the motor domain of non-muscle myosin heavy chain-IIA, and these patients had poorer kidney survival than those with variants affecting the tail domain (P = 0.02). There was no significant difference in kidney survival between patients treated with and without RAS inhibitors. Hemodialysis and peritoneal dialysis were performed in 16 and 7 patients, respectively. There were no major bleeding complications during the perioperative period or during follow-up, except for one patient. Most of the 11 patients who underwent kidney transplantation required perioperative red cell concentrate transfusions, but there was no graft loss during the median posttransplant observational period of 2.0 (interquartile range, 1.3-6.8) years.

CONCLUSION

Our study demonstrated no beneficial effect of RAS inhibitors on kidney function in patients with MYH9-RD, indicating the need for further studies with more patients. All modalities of KRT are feasible options for MYH9-RD patients who progress to ESKD, with adequate attention to bleeding complications.

Successful administration of eltrombopag in preparation for peritoneal dialysis catheter placement in a girl with MYH9-related disease

MYH9-related disease is an autosomal dominant disorder characterized by macrothrombocytopenia, nephropathy, inclusion bodies in leukocytes, sensorineural hearing loss, and cataract. Severe cases require kidney replacement therapy in the patient's second decade of life; thrombocytopenia constitutes a major risk factor for hemorrhagic complications during dialysis initiation or kidney transplantation. Prophylactic platelet transfusion prior to surgery is commonly administered to affected patients in these cases. However, transfusion in such patients has limitations other than the general risk of allergic reactions and blood-borne infections; it may also trigger alloimmunization, leading to platelet transfusion resistance or the development of anti-donor antibodies in potential kidney transplant recipients. Here, we describe prophylactic administration of eltrombopag, an oral thrombopoietin receptor agonist, prior to laparoscopic peritoneal dialysis catheter placement in a 15-year-old girl with MYH9-related disease. Her platelet count was approximately 30 × 103/μL at baseline; it increased to 61 × 103/μL on the day before surgery, thereby avoiding the need for platelet transfusions. There were no major bleeding or adverse events associated with eltrombopag administration. Thus, eltrombopag may be a safe and effective alternative to prophylactic platelet transfusions in patients with MYH9-related disease.

Anesthetic Management of Living-Donor Renal Transplantation in a Patient With Epstein Syndrome Using Rotational Thromboelastometry: A Case Report

Epstein syndrome is a myosin heavy chain 9 (MYH9)-related disorder characterized by hearing loss and macrothrombocytopenia with renal failure, which usually requires platelet transfusion during surgery. We report the case of a 22-year-old man who underwent living-donor renal transplantation without platelet transfusion using rotational thromboelastometry (ROTEM) monitoring. His intraoperative laboratory coagulation findings were a platelet count of 28–31 × 10⁹/L based on microscopy and fibrinogen of 256 mg/dL. However, his extrinsic pathway evaluations by ROTEM were normal. The estimated blood loss during the operation was 150 mL, and the patient showed no bleeding complications without platelet transfusion.

Renin-angiotensin System Blockade Therapy for Early Renal Involvement in MYH9-related Disease with an E1841K Mutation

MYH9-related disease is a rare genetic disorder characterized by macrothrombocytopenia, with frequent proteinuric nephropathy, hearing loss, and cataract. Although proteinuric nephropathy usually progresses to renal failure, there is no established treatment for the nephropathy. We herein describe the case of a 19-year-old man carrying an E1841K MYH9 mutation, who developed persistent proteinuria. The patient was diagnosed with early-stage MYH9-related nephropathy based on the histological examination of a kidney biopsy specimen. The patient was treated with enalapril, which significantly reduced the proteinuria with no decline in his renal function. The early administration of renin-angiotensin system blockade therapy may have beneficial effects on MYH9-related nephropathy in patients with E1841K mutations. We also briefly summarize previously published cases of MYH9-related nephropathy treated with renin-angiotensin system (RAS) blockade therapy.

MYH9-related disease: it does exist, may be more frequent than you think and requires specific therapy

In this issue of ckj, Tabibzadeh et al. report one of the largest series of patients with MYH9 mutations and kidney disease. The cardinal manifestation of MYH9-related disease is thrombocytopenia with giant platelets. The population frequency of pathogenic MYH9 mutations may be at least 1 in 20 000. The literature abounds in misdiagnosed cases treated for idiopathic thrombocytopenic purpura with immune suppressants and even splenectomy. Additional manifestations include neurosensorial deafness and proteinuric and hematuric progressive kidney disease (at some point, it was called Alport syndrome with macrothrombocytopenia), leucocyte inclusions, cataracts and liver enzyme abnormalities, resulting in different names for different manifestation combinations (MATINS, May-Hegglin anomaly, Fechtner, Epstein and Sebastian syndromes, and deafness AD 17). The penetrance and severity of kidney disease are very variable, which may obscure the autosomal dominant inheritance. A correct diagnosis will both preclude unnecessary and potentially dangerous therapeutic interventions and allow genetic counselling and adequate treatment. Morphological erythrocyte, granulocyte and platelet abnormalities may allow the future development of high-throughput screening techniques adapted to clinical peripheral blood flow cytometers.