ELSEV IER zyxwvutsrqp Multicenter Genetic Study of Retinitis Pigmentosa in Japan: II. Prevalence of Autosomal Recessive Retinitis Pigmentosa Mutsuko Hayakawa,* Keiko Fujiki,* Atsushi Kanai,* Miyo Matsumura,+ Yoshihito Honda,? Hiroshi Sakaue,’ Makoto Tamai,’ Takehiko Sakuma,* Takashi Tokoro,$ Tomotsugu Yura,§ Nobue KubotaJ Shinichiro Kawano,il Mizuo Matsui,’ Mitsuko Yuzawa,q Yoshihisa Oguchi,# Kiyoshi Akeo, Emiko Adachi,** Tsuyoshi Kimura,** Yozo Miyake,++ Masayuki Horiguchi,+t Kenji Wakabayashi, $$ Nobuto Ishizaka,*$ Kan Koizumi,@ Masanobu Uyama)ll Nobuko Tagami)lll Tatsuro Ishibashi,lq Takakazu Honda,” Takashi Nakagawa,## Muneyasu Takeda,## Kanji Choshi,*** Michio Watanabe,*** Osamu Tamura,+tt Naomi Shimowake,tit Hisayuki Ueno,sss Kazuyuki Yoshida,“ s$ Yasushi Isashiki”@ and Norio Ohbas@ zyxwvutsrqponmlkjihgfedcbaZYXWVU Departments of Ophthalmology ofi *Juntendo University School of Medicine, fKyoto University School of M edicine, $Tohoku University School of M edicine, “ Tokyo M edical and Dental University, /Teikyo University School of Medicine, ¶Nihon University School of Medicine, ‘Keio University School of Medicine, **Chiba University School of Medicine, ttNagoya University School of Medicine, $$Kanazawa University School of Medicine, f§Hyogo Prefectural Amagasaki Hospital, IlKansai Medical University, R¶Kyushu University School of M edicine, “ Sapporo Medical University, *‘*Hiroshima University School of Medicine, tttEhime University School of M edicine, j$*Kochi M edical School, § @ Kagoshima University Faculty of M edicine Abstract: Retinitis pigmentosa (RP) is a group of genetically heterogeneous diseases with autosomal recessive (AR), autosomal dominant, and X-linked modes of inheritance. Autosomal recessive retinitk pigmentosa (ARRP) is the most common form in Japan. A genetic analysis was done to determine the prevalence of ARRP indirectly, to provide an estimation of changing trends in the overall prevalence of RP. Data on the frequency of consanguinity and marriage year of normal parents of 59 ARRP patients were obtained from a nationwide multicenter survey of typical retinitis pigmentosa conducted in 1990. The gene frequency of ARRP was 0.01145 (Dahlberg’s formula). In 1990, the number of young symptomatic ARRP patients de- creased, while the number of patients aged 40 years and older increased. The total number of symptomatic ARRP patients in 1990 was nearly 21% higher than in 1970. Despite a dramatic decline in consanguinity in recent decades in Japan, the number of ARRP patients has in- creased. This increase is attributed to greater longevity and overall population growth. Our results suggest that the total number of RP patients has not decreased, and may even have increased. Jpn J Ophthalmol1997;41:7-11 0 1997 Japanese Ophthalmological Society Key Words: Autosomal recessive inheritance, consanguineous marriage, gene frequency, inbreeding coefficient, prevalence, retinitis pigmentosa. Received: June lo,1996 Address correspondence and reprint requests to: Mutsuko Introduction HAYAKAWA, MD, Department of Ophthalmology, Juntendo University School of Medicine, 3-l-3, Hongo, Bunkyo-ku, Tokyo 113, Japan Typical retinitis pigmentosa (RP) is one of the ma- jor causes of visual loss in advanced countries. It is a Jpn J Ophthalmol41,7-ll(l997) 0 1997 Japanese Ophthalmological Society Published by Elsevier Science Inc. 0021-5155/97/$17.00 PII SoOZl-5155(96)WO19-6