Hey guys! Thanks for playing along with yesterday’s MMM. The answer is Autosomal Recessive Polycystic Kidney Disease (ARPKD) – congratulations to Federica, Erin, Dave, F, Francine, Rich S, NG and RF for nailing this tricky diagnosis!
ARPKD is exactly what the name implies: a congenital form of polycystic kidney disease. Although it is known that mutations in the PKHD1 gene cause ARPKD, the clinical presentation of this disease can be highly variable. Affected children are born with kidneys that do not function properly because of cystic dilations of the renal collecting ducts. As in the example I gave yesterday, up to 50% of affected neonates have (and many die of) pulmonary hypoplasia. The massively enlarged kidneys limit the movement of the diaphragm, resulting in hypoventilation and ultimately respiratory failure. Severe cases also often present with Potter syndrome, a constellation of abnormal physical findings including club feet, hip dislocation, snubbed nose, low-set and flattened ears, recessed chin, and deep eye creases. Potter’s syndrome results from what is called “oligohydraminos”. Oligohydraminos is a term that is used when there is less than an ideal amount of amniotic fluid in utero. Fetal urination significantly contributes to the volume of amniotic fluid so an infant with ARPKD, who can’t produce adequate urine because of kidney dysfunction, might show signs of morphogenesis secondary to the severe decrease in amniotic fluid volume.
As ultrasound screenings have become increasingly routine, most cases of ARPKD are detected prenatally. Children who survive the first month have as much of an 80% chance of living beyond 15 years of age, but do tend to show progressive increases in renal dysfunction. The liver is the other major organ that is involved in ARPKD. Currently there are no specific interventions that prevent or delay the loss of kidney function in ARPKD. Management includes supportive therapy for neonates with respiratory distress and eventually renal replacement therapy (dialysis) in older patients.
I have a big renal final exam on Friday so I’m going to get back to studying for now. Have a good rest of the week, everyone!