Diagnosis and treatment of multisystem amyloidosis associated with SGPL1 mutation: A case report and review of the literature.

RATIONALE: Amyloidosis is a rare, clinically heterogeneous disease, which makes its diagnosis difficult. The relationship between amyloidosis and gene mutations is insufficiently understood. We report a case of sphingosine-1-phosphate lyase 1 (SGPL1) mutation-related amyloidosis, and review the related literature. PATIENT CONCERNS: A 53-year-old man was admitted to our hospital with a 5-month history of renal dysfunction and abdominal distension, aggravated since 2 days. Five months ago, the patient was diagnosed with nephrotic syndrome, with liver dysfunction and abdominal distension. His symptoms improved after treatment with methylprednisolone sodium succinate, dipyridamole, hydroxychloroquine sulfate, and ursodeoxycholic acid. Two days ago, his abdominal distension worsened, and was not associated with eating, acid reflux, heartburn, fatigue, or poor appetite. A physical examination showed periumbilical ecchymosis and hepatic enlargement. Blood biochemistry showed kidney dysfunction, dyslipidemia, increased alkaline phosphatase and glutamyltransferase, and decreased albumin. A urine protein test was positive. A liver biopsy showed chronic hepatitis and positive Congo red staining. Serum and urine immunofixation electrophoresis showed increased monoclonal IgA-κ protein. Color echocardiography and magnetic resonance imaging showed left ventricular wall thickening and slight pericardial effusion. Sanger sequencing showed a heterozygous, autosomal recessive mutation in the SGPL1 gene (blood). In our patient, amyloidosis was attributed to increased monoclonal IGA-κ protein production by plasma cells after SGPL1 mutation. DIAGNOSIS: Primary amyloidosis with multisystem involvement (liver, heart, and kidneys). INTERVENTIONS: The patient was administered dipyridamole (25 mg, po, tid), methylprednisolone (40 mg, po, qd, gradually reduced over 6 months), hydroxychloroquine sulfate (200 mg, po, bid), and ursodeoxycholic acid (250 mg, po, tid) until his renal and hepatic markers improved. Immunomodulatory therapy was adjusted according to the patient's response, and the final regimen was bortezomib injection (1.8 mg, sc, once a week), cyclophosphamide (0.4 g, po, once a week), and dexamethasone (20 mg, po, twice a week), which is currently ongoing. OUTCOME: Immunomodulatory therapy improved and stabilized the patient's condition. LESSONS: SGPL1 mutation may cause multisystem amyloidosis by disrupting S1P homeostasis and increasing monoclonal IGA-κ protein production, leading to amyloidosis. This case highlights the importance of genetic screening and an improved understanding of SGPL1 gene mutations.