Alkaptonuria is a rare, autosomal recessive disorder of tyrosine degradation due to deficiency of the third enzyme in the catabolic pathway. As a result, homogentisic acid (HGA) accumulates and is excreted in gram quantities in the urine, which turns dark upon alkalization. The first symptoms, occurring in early adulthood, involve a painful, progressively debilitating arthritis of the spine and large joints. Cardiac valvular disease and renal and prostate stones occur later. Previously suggested therapies have failed to show benefit, and management remains symptomatic. Nitisinone, a potent inhibitor of the second enzyme in the tyrosine catabolic pathway, is considered a potential therapy; proof-of-principle studies showed 95% reduction in urinary HGA. Based on those findings, a prospective, randomized clinical trial was initiated in 2005 to evaluate 40 patients over a 36-month period. The primary outcome parameter was hip total range of motion with measures of musculoskeletal function serving as secondary parameters. Biochemically, this study consistently demonstrated 95% reduction of HGA in urine and plasma over the course of 3 years. Clinically, primary and secondary parameters did not prove benefit from the medication. Side effects were infrequent. This trial illustrates the remarkable tolerability of nitisinone, its biochemical efficacy, and the need to investigate its use in younger individuals prior to development of debilitating arthritis.

BACKGROUND & AIMS Autosomal recessive polycystic kidney disease (ARPKD), the most common ciliopathy of childhood, is characterized by congenital hepatic fibrosis and progressive cystic degeneration of kidneys. We aimed to describe congenital hepatic fibrosis in patients with ARPKD, confirmed by detection of mutations in PKHD1. METHODS Patients with ARPKD and congenital hepatic fibrosis were evaluated at the National Institutes of Health from 2003 to 2009. We analyzed clinical, molecular, and imaging data from 73 patients (age, 1–56 years; average, 12.7 ± 13.1 years) with kidney and liver involvement (based on clinical, imaging, or biopsy analyses) and mutations in PKHD1. RESULTS Initial symptoms were liver related in 26% of patients, and others presented with kidney disease. One patient underwent liver and kidney transplantation, and 10 others received kidney transplants. Four presented with cholangitis and one with variceal bleeding. Sixty-nine percent of patients had enlarged left lobes on magnetic resonance imaging, 92% had increased liver echogenicity on ultrasonography, and 65% had splenomegaly. Splenomegaly started early in life; 60% of children younger than 5 years had enlarged spleens. Spleen volume had an inverse correlation with platelet count and prothrombin time but not with serum albumin level. Platelet count was the best predictor of spleen volume (area under the curve of 0.88905), and spleen length corrected for patient’s height correlated inversely with platelet count (R2 = 0.42, P < .0001). Spleen volume did not correlate with renal function or type of PKHD1 mutation. Twenty-two of 31 patients who underwent endoscopy were found to have varices. Five had variceal bleeding, and 2 had portosystemic shunts. Forty-percent had Caroli syndrome, and 30% had an isolated dilated common bile duct. CONCLUSIONS Platelet count is the best predictor of the severity of portal hypertension, which has early onset but is underdiagnosed in patients with ARPKD. Seventy percent of patients with ARPKD have biliary abnormalities. Kidney and liver disease are independent, and variability in severity is not explainable by type of PKHD1 mutation;

ARPKD/CHF is an inherited disease characterized by non-obstructive fusiform dilatation of the renal collecting ducts leading to enlarged spongiform kidneys and ductal plate malformation of the liver resulting in congenital hepatic fibrosis. ARPKD/CHF has a broad spectrum of clinical presentations involving the kidney and liver. Imaging plays an important role in the diagnosis and follow-up of ARPKD/CHF. Combined use of conventional and high-resolution US with MR cholangiography in ARPKD/CHF patients allows detailed definition of the extent of kidney and hepatobiliary manifestations without requiring ionizing radiation and contrast agents.