A Rare Cause of Retroperitoneal Fibrosis in Adults: H Syndrome Presenting After 35 Years- A Case Report.

INTRODUCTION: Retroperitoneal  fibrosis  (RPF)  is  a  rare  fibro- inflammatory  disorder  that  may  cause  urinary  tract  obstruction and renal failure. Although most RPF cases are IgG4-related, rare genetic conditions can also contribute to the disease. H syndrome, an  autosomal  recessive  disorder  caused  by  biallelic  SLC29A3 mutations, usually presents in childhood with cutaneous, endocrine, and systemic manifestations; adult onset is exceptionally rare.

CASE PRESENTATION: A 36-year-old woman was admitted to hospital with the complaint of nausea, vomiting, and oliguria. Laboratory tests showed urea 116 mg/dL, creatinine 5,8 mg/dL,. Non-contrast computed tomography imaging revealed bilateral hydronephrosis and a 2,5 cm retroperitoneal fibrotic mass encasing the abdominal aorta and iliac arteries. Extensive evaluation-including positron emission tomography, lymph-node histology, and autoimmune/ IgG4 serology-found no evidence of malignancy, infection, or IgG4- related  disease.  Family  history  disclosed  parental  consanguinity and  a  brother  with  H  syndrome.  Next-generation  sequencingidentified  a  homozygous  SLC29A3  (NM_018344.5):c.1339G > A (p.Glu447Lys) mutation, confirming H syndrome. Bilateral ureteral stenting  and  corticosteroid  therapy  led  to  full  renal  recovery (creatinine 0.7 mg/dL).

CONCLUSION: This case expands the clinical spectrum of H syndrome by  documenting  late-onset  RPF  without  typical  dermatologic  or auditory  signs.  Recognition  of  familial  risk  and  timely  genetic testing  were  decisive  for  diagnosis.  Early  decompression  and immunosuppression  preserved  renal  function.  Reporting  suchatypical  presentations  increases  awareness  of  H  syndrome  as  a rare  genetic  cause  of  RPF  and  supports  comprehensive  genetic evaluation in adults with unexplained retroperitoneal fibrosis.