Type II tyrosinaemia is a rare autosomal recessive disorder where there is raised blood tyrosine.
Tyrosinemia type II (also known as oculocutaneous tyrosinemia and Richner-Hanhart syndrome)
- is a rare distinctive disorder with autosomal recessive inheritance, characterized by skin and eye lesions, and occasionally learning disability (2)
- approximately half of the hitherto reported cases are of Italian descent
- is distinct from the more severe hepatorenal tyrosinemia (tyrosinemia type I) and from benign transient tyrosinemia of the new-born
- caused by a deficiency of the hepatic enzyme tyrosine aminotransferase (TAT), which leads to increased levels of tyrosine in the blood and urine
- TAT gene is located on the long arm of chromosome 16, the exact locus being 16q22-24
- Tyrosinemia type II with features confined to the skin has been reported previously
- typical dermatologic findings are painful, well-demarcated hyperkeratosis on the palms and soles, although the palms can be unaffected
- on the palms the distribution usually involves the fingertips, and the thenar and hypothenar eminences, while the lesions on the soles are on the weight-bearing areas
- lesions may begin as bullae and erosions that progress to crusted, hyperkeratotic plaques, are often associated with hyperhydrosis
- age at onset of skin lesions can range from the first week of life to the second decade.
- ocular manifestations
- can develop as early as the first day of life and alternatively may present for the first time as late as the fourth decade
- early signs are photophobia, pain, tearing and redness, while late signs include corneal clouding and central or paracentral opacities, superficial or deep dendritic ulceration, corneal neovascularization, and corneal scars
Management of tyrosinemia type II is largely by dietary restriction to food low in tyrosine and phenylalanine, which reverses ocular and cutaneous abnormalities
Reference:
- Al-Ratrout JT, Al-Muzian M, Al-Nazer M, Ansari NA. Plantar keratoderma: a manifestation of tyrosinemia type II (Richner-Hanhart syndrome). Ann Saudi Med. 2005;25(5):422-424. doi:10.5144/0256-4947.2005.422
- Locatelli F, Puzenat E, Arnoux JB, Blanc D, Aubin F. Richner-Hanhart syndrome (tyrosinemia type II). Cutis. 2017 Dec;100(6):E20-E22. PMID: 29360903.