#3140 THE WEST OF SCOTLAND AND THROMBOTIC MICROANGIOPATHY
Authors: Groome Ciaran , Padmanabhan Neal 
Published: June 2023

Abstract

Background and Aims
Thrombotic microangiopathy (TMA) is a diagnosis made on tissue biopsy manifesting as acute organ dysfunction. It has a variety of causes broadly categorised as: primary hereditary/genetic, primary acquired, secondary, and infection-related [1]. On blood testing there is evidence of microangiopathic haemolytic anaemia (MAHA) –, thrombocytopenia, raised lactate dehydrogenase (LDH), reduced haptoglobin and fragments on blood film. Renal involvement with acute injury is evidenced by an elevation in creatinine; together with MAHA this is haemolytic uraemic syndrome (HUS). We sought to examine the TMA/MAHA population as it presented to nephrology in the West of Scotland and evaluate if there was differences in presentation between TMA with and without MAHA.

Method
This is a retrospective case series of adult nephrology patients. We extracted health data from the west of Scotland renal electronic patient records database Strathclyde Electronic Renal Patient Record (“SERPR”) provided by VitalDataClient. We ran a query to identify patients in whom TMA and/or MAHA and/or HUS was inputted as a diagnosis. 363 patients were identified. Each was manually inspected. Patients were excluded who were not suitable for inclusion (e.g. paediatric data, incomplete records, patients without relevant diagnoses). Non-parametric Kruskal Wallis testing was used via R statistical software.

Results
134 patients were identified. The underlying diagnoses were: hypertension (n = 34), the atypical HUS (aHUS, n = 22), drug-induced (n = 17), autoimmune (n = 12,), thrombotic thrombocytopenic purpura (n = 12), malignancy (n = 10), inflammatory (n = 10), peri-partum (n = 9). Others included: transplant-related, unknown, Ecoli 0157, diarrhoea-related, IgA, AAV, MPGN, and essential thrombocythaemia. Note: many patients had multiple possible contributors to their diagnosis. The average biochemical levels at presentation were: creatinine 591umol/L; haemoglobin 82; platelet count 98.7; LDH 1674.2; bilirubin 34.5. Renal recovery was observed in n = 27 (19%); CKD3 n = 32 (24%); CKD4 n = 10(7%); CKD5 n = 7(5%); those who have progressed to ESRF (requiring renal replacement therapy) n = 40(31%); persisting transplant function n = 5(4%). 15 patients died (10%). We categorised patients into 3 groups. 1 – presence of TMA on biopsy without MAHA (n = 28). 2 – TMA on biopsy plus evidence of MAHA (n = 41). And 3 – MAHA in those not biopsied (n = 62). 3 patients with MAHA did not have TMA on biopsy. Those in group 1 had on average a lower serum creatinine at 331umol/L compared with group 2 (634 umol/L) and group 3 (666 umol/L). This result was significant p &lt;0.05. Hypertension was a leading cause in groups 1 and 2. aHUS was not present in group 1 - all patients presented with MAHA. All peri-partum patients were in group 3 i.e. not biopsied.

Conclusion
It is evident from the dataset that hypertension is a major contributor to acute and chronic renal impairment. With aHUS contributing to a significant number of cases, given the advances in testing and therapeutics, early liaison with national services in complement disorders is paramount to protecting the kidneys. With 19% of patients regaining an eGFR &gt;60ml/min prompt investigation is crucial to reducing the burden of disease. Long term renal follow-up should be offered. 21% of patients had no evidence of MAHA –we should be wary of excluding a TMA process in the absence of MAHA.