Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disease that displays genetic heterogeneity; there are 9 known subtypes. HPS is characterized by oculocutaneous albinism, a platelet storage pool deficiency and resultant bleeding diathesis, and lysosomal accumulation of ceroid lipofuscin. Patients with HPS, specifically those with the genotypes HPS-1, HPS-2, or HPS-4, are predisposed to interstitial lung disease. In addition, some patients with HPS develop granulomatous colitis. Optimal health care requires a thorough knowledge of the unique health risks and functional limitations associated with this syndrome.

α-Intercalated cells (A-ICs) within the collecting duct of the kidney are critical for acid-base homeostasis. Here, we have shown that A-ICs also serve as both sentinels and effectors in the defense against urinary infections. In a murine urinary tract infection model, A-ICs bound uropathogenic E. coli and responded by acidifying the urine and secreting the bacteriostatic protein lipocalin 2 (LCN2; also known as NGAL). A-IC-dependent LCN2 secretion required TLR4, as mice expressing an LPS-insensitive form of TLR4 expressed reduced levels of LCN2. The presence of LCN2 in urine was both necessary and sufficient to control the urinary tract infection through iron sequestration, even in the harsh condition of urine acidification. In mice lacking A-ICs, both urinary LCN2 and urinary acidification were reduced, and consequently bacterial clearance was limited. Together these results indicate that A-ICs, which are known to regulate acid-base metabolism, are also critical for urinary defense against pathogenic bacteria. They respond to both cystitis and pyelonephritis by delivering bacteriostatic chemical agents to the lower urinary system.

A r t i c l e A m e n d m e n t s5 5 2 1

No abstract

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessively inherited disorder consisting of the triad of oculocutaneous tyrosinase-positive albinism, prolonged bleeding time secondary to platelet storage pool defect and ceroid depositions within the reticuloendothelial system. Some patients also reportedly have gastrointestinal (GI) complications related to chronic granulomatous colitis, enterocolitis and extensive granulomatous perianal disease, the later previously unreported in the literature. These observations suggest that the GI complications of HPS are due to the development of classical Crohn's disease. The implications for disease pathogenesis and surgical management are discussed.