We studied the pathogenetic role of iminodipeptides, and the effects of
corticosteroids on the skin lesions of two adult female siblings with
prolidase deficiency. The elder sister had had severe
skin ulcers and
mental retardation since childhood, while the younger sister had shown milder clinical manifestations since late adolescence. The
ulcers showed vascular wall thickening and neutrophil infiltration. Oral
prednisolone at moderate doses was not effective, but
corticosteroid pulse
therapy followed by a moderate dose of
prednisolone improved the preulcerative indurated lesions and
ulcers. A 2-year follow-up of the younger patient indicated that
N-formyl methionyl leucyl phenylalanine-induced neutrophil
superoxide generation was elevated, in parallel with an increase in the serum iminodipeptide level, when the
skin ulcers and preulcerative indurated lesions were most active.
Corticosteroid pulse
therapy downregulated the
superoxide generation by neutrophils. The serum iminodipeptide level, however, did not decrease during 25 days after pulse
therapy. These findings suggest that iminodipeptides may play an important part in aggravating the skin lesions by priming neutrophil
superoxide generation, and that high-dose
corticosteroids improve the skin lesions, probably by inhibiting the infiltration, and
superoxide generation by, neutrophils. Neutrophil
superoxide generation was more prominent in the elder sister, suggesting that clinical severity may depend on the response of neutrophils to the iminodipeptides. Chronic stimulation by
superoxide may cause thickening of cerebral blood vessels and eventual
mental retardation.