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Hermansky-Pudlak syndrome with pulmonary fibrosis
Hermansky-Pudlak syndrome with pulmonary fibrosis as a complication includes two types (HPS-1 and HPS-4) of Hermansky-Pudlak syndrome (HPS; see this term), a multi-system disorder characterized by oculocutaneous albinism, bleeding diathesis and, in some cases, pulmonary fibrosis or granulomatous colitis.
Prevalence of all types of HPS is estimated at between 1/500,000 and 1/1,000,000 in non-Puerto Rican populations. In northwestern Puerto Rico the prevalence of HSP-1 is 1/1,800 due to a founder effect. HSP-1 is reported in sporadic patients worldwide; founder effects have (apart from Puerto Rico) also been reported in a small isolate in a Swiss village and in Japan. Prevalence of HSP-4 is unknown, but to date around 20 patients have been described worldwide.
HPS-1 and HPS-4 present with features of HPS including oculocutaneous albinisim, reduced visual acuity, horizontal nystagmus, easy bruising of soft tissues, epistaxis, and prolonged bleeding after dental extraction, surgery or childbirth. Women may present with medically significant menstrual bleeding. Complications of HPS may include granulomatous colitis and pulmonary fibrosis. Pulmonary fibrosis is the most serious complication of HPS-1 and HPS-4 and usually presents in the fourth or fifth decade.
HPS-1 is caused by mutations in the HPS1 gene (10q23.1) and HPS-4 is caused by mutations in the HPS4 gene (22q11.2-q12.2). The gene products, HPS1 and HPS4, are part of the multi-subunit complex BLOC-3 (biogenesis of lysosome-related organelles complex 3).
HPS1 and HPS4 are both transmitted in an autosomal recessive manner.
Management and treatment
Lung transplant is the only known treatment for pulmonary fibrosis in HPS-1 and HPS-4. Pirfenidone may slow progression but only in patients who have significant residual lung function. Steroid therapy is not effective.
Prognosis is poor as the pulmonary fibrosis is fatal.