Atypical Clinical Presentation of Autosomal Recessive Polycystic Kidney Mimicking Medullary Sponge Kidney Disease

A case of diffuse kidney hyperechogenicity in early childhood associated with biallelic PKHD1 variants

BACKGROUND

Nephrocalcinosis (NC) is characterized by an excessive accumulation of calcium deposits in the kidneys. In children, it is often incidentally discovered with an uncertain prognosis.

CASE-DIAGNOSIS/TREATMENT

A 3-month-old girl suspected to have a milk protein allergy underwent an ultrasound that revealed increased echogenicity in the kidney pyramids suggestive of medullary NC. At the age of 18 months, imaging findings revealed not only hyperechogenicity in the medulla but also in the cortex. Over the course of a long follow-up, her kidneys maintained size within the upper limits but showed an increase by age 7. Genetic analysis identified PKHD1 variants, which required structural predictive tools to guide clinical diagnosis. Until the age of 7, her kidney function has remained intact; however, her prognosis is uncertain.

CONCLUSIONS

NC in newborns is a rare condition, but its incidence is rising. Recurrent urinary infections or kidney stones may lead to kidney failure. A proactive approach in sporadic NC enables an early diagnosis to orientate clinical supervision and facilitates counseling to support family planning decisions.

Medullary Sponge Kidney and Its Relationship with Primary Distal Renal Tubular Acidosis: Case Reports and a Comprehensive Genetics-First Approach

Medullary sponge kidney (MSK) is a description of radiographic features. However, the pathogenesis of MSK remains unclear. MSK is supposed to be the cause of secondary distal renal tubular acidosis (dRTA), although there are case reports suggesting that MSK is a complication of primary dRTA. In addition to these reports, we report 3 patients with metabolic acidosis and MSK, in whom primary dRTA is confirmed by molecular genetic analyses of SLC4A1 and ATP6V1B1 genes. With a comprehensive genetics-first approach using the 100,000 Genomes Rare Diseases Project dataset, the association between MSK and primary dRTA is examined. We showed that many patients with MSK phenotypes are genetically tested with a gene panel which does not contain dRTA-associated genes, revealing opportunities for missed genetic diagnosis. Our cases highlight that the radiological description of MSK is not a straightforward disease or clinical phenotype. Therefore, when an MSK appearance is noted, a broader set of causes should be considered including genetic causes of primary dRTA as the underlying reason for medullary imaging abnormalities.

Autosomal Recessive Polycystic Kidney Disease: Diagnosis, Prognosis, and Management

Autosomal recessive polycystic kidney disease (ARPKD) is the rare and usually early-onset form of polycystic kidney disease with a typical clinical presentation of enlarged cystic kidneys and liver involvement with congenital hepatic fibrosis or Caroli syndrome. ARPKD remains a clinical challenge in pediatrics, frequently requiring continuous and long-term multidisciplinary treatment. In this review, we aim to give an overview over clinical aspects of ARPKD and recent developments in our understanding of disease progression, risk patterns, and treatment of ARPKD.