Ochronose endogène (alcaptonurie)

• Endogenous ochronosis (also called alcaptonuria) is a rare autosomal regressive disorder where there is enzymatic deficiency of homongentisic acid oxydase (AHG).
• This results in accumulation of AHG which is oxydized and polymerized in a substance close to melanin called benzoquinone acetic acid (ABQA). Its accumulation in the skin results in the clinical pigmentation.

• The authors report the case of a 43 year  old man with Alport’s syndrome with terminal kidney failure.
• He presented with pigmentation on the skin localized on the face (more precisely in the malar, nasal, perioral areas).
• Histological examination confirmed endogenous ochronosis with elevation of AHG on chromatography.
• After a period of dialysis performed three times weekly, he underwent kidney transplant…if was followed over several years by fading of pigmentation, even completely disappearing in some areas.

• The authors explained the improvement in the following way:
  • AHG comes normaly from the catabolism of tyrosine and it is elimated by the kidney.
  • Before the transplant, absent kidney glomeruli resulted in the building up of AHG.
  • The kidney transplant enabled to restore functional glomeruli and the elimination of AHG.

• Exogenous Ochronosis is not as frequent as endogenous ochronosis (which comes from hydroquinone excess use).
• This interesting case report shows that endogenous ochronosis can be regressive once the metabolites are removed. Like endogenous ochronosis, although the improvement can be substantial once the offending parameter is removed, it appears not tom be complete.

Cluzel C. et al. Un cas d’ochronose endogène régressive après greffe rénale. 2013 (12) – Journees Dermatologiques de Paris (JDP)