A 40-year-old man attended the emergency department due to the appearance of oedema. He had a family history of a mother with unrelated renal amyloidosis. The mother's renal biopsy report refers to permanganate resistance, which seems to rule out AA amyloidosis, and leads us to consider, at the time the diagnosis was made, the possibility of AL amyloidosis.
The patient is not receiving any pharmacological treatment. Physical examination revealed blood pressure of 135/75 mmHg and bimalleolar oedema, with no other data of interest. Laboratory tests confirmed the presence of nephrotic syndrome (serum albumin 2.5 g/dl, cholesterolaemia 275 mg/dl and proteinuria 6 g/24 h), with no alterations in the sediment and normal glomerular filtration rate. The electrophoretic spectrum in blood and urine, the immunological study and renal ultrasound were normal. A renal biopsy was performed, showing 19 glomeruli with a totally distorted structure due to a nodular hyaline deposit, with positivity for Congo red and thioflavin; the tubules and vessels showed no significant alterations, the result being compatible with amyloidosis. In the study on the paraffin sample, there was marked positivity for AP protein, which is a part of the amyloid substance common in all types of amyloidosis, with negativity for light chains and AA, B2 microglobulin and transthyretin proteins. A complementary study was performed with antibodies against fibrinogen and lysozyme, and the amyloid substance deposits were positive for the A alpha chain of fibrinogen (Afib). However, the genetic study found no mutation in the Afib chain gene, but demonstrated a previously undescribed mutation in the apolipoprotein AI (apo AI) gene. In view of this discrepancy, the biopsy of the mother was analysed and showed glomerular deposition in the cortex and massive deposition at the medullary level. Deposition at the medullary level is not described in Afib amyloidosis, being very characteristic of apo AI. It is concluded that the initial results of immunohistochemistry are not reliable because they were not performed under the appropriate conditions, and the presence of apo AI was subsequently confirmed by the same technique.
An extension study was performed, with echocardiography and electromyography, with no evidence of cardiac involvement or autonomic neuropathy. A progressive increase in transaminases was detected, suggestive of liver involvement. These results are consistent with this type of familial amyloidosis, with preferential renal and hepatic involvement. Despite the initial normality, renal function progressively deteriorated to the point of requiring renal replacement therapy within 2 years. The patient was treated with peritoneal dialysis for 4 years until he underwent surgery and a cadaver donor kidney transplant. He had a complicated postoperative period with splenic rupture, in the context of his disease, with amyloid deposition in the spleen, requiring an urgent splenectomy. Finally, the patient was discharged in stable condition.