Atypical hemolytic uremic syndrome (aHUS), a rare form of thrombotic microangiopathy, is distinguished from the typical form by the absence of a preceding verotoxin-producing Escherichia coli infection. Notably, aHUS occurs in association with genetic or acquired disorders causing dysregulation of the alternative complement pathway. Patients with aHUS may show the presence of anti-complement factor H (CFH) autoantibodies. This acquired form of aHUS (anti-CFH-aHUS) primarily affects children aged 9–13 years. We report a case of a 13-year-old Lao girl with clinical features of aHUS (most likely anti-CFH-aHUS). The initial presentation of the patient met the classical clinical triad of thrombotic microangiopathy (microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury) without preceding diarrheal illness. Low serum levels of complement 3 and normal levels of complement 4 indicated abnormal activation of the alternative complement pathway. Plasma infusion and high-dose corticosteroid therapy resulted in improvement of the renal function and hematological profile, although the patient subsequently died of infectious complications. This is the first case report that describes aHUS (possibly anti-CFH-aHUS) in Laos.
Adolescent ; Anemia, Hemolytic ; Atypical Hemolytic Uremic Syndrome ; Autoantibodies ; Child ; Complement C3 ; Complement C4 ; Complement Factor H ; Complement Pathway, Alternative ; Female ; Humans ; Immunosuppression ; Kidney ; Laos ; Plasma ; Shiga-Toxigenic Escherichia coli ; Thrombocytopenia ; Thrombotic Microangiopathies

Distal renal tubular acidosis (dRTA) is a rare renal tubular disorder characterized by normal anion gap metabolic acidosis, hypokalemia, and high urine pH. It can be inherited or acquired. In untreated pediatric patients with dRTA, rickets and growth retardation are common. We report the case of a 12-year-old Lao girl who presented with typical clinical features of dRTA with severe bone deformities that developed after a bed-ridden state due to a bicycle accident at the age of 8 years. Initial laboratory tests revealed metabolic acidosis with a normal anion gap, hypokalemia, and alkali urine. Renal ultrasonography revealed bilateral medullary nephrocalcinosis. Whole exome sequencing revealed no pathogenic mutations. After treatment with oral alkali, potassium, and vitamin D, she could walk and run. Later, she underwent corrective orthopedic surgeries for bony deformities. Thus, in pediatric dRTA patients, despite severe symptoms remaining untreated, accurate diagnosis and proper management can improve quality of life.