CATERPILLAR BODIES OF PORPHYRIA-CUTANEA-TARDA ULTRASTRUCTURALLY REPRESENT A UNIQUE ARRANGEMENT OF COLLOID AND BASEMENT-MEMBRANE BODIES

Caterpillar bodies are eosinophilic, periodic acid-Schiff (PAS)-positi ve globules arranged in a linear fashion in the epidermis overlying su bepidermal blisters of porphyria cutanea tarda (Am J Dermatopathol 199 3;15:199-202). We retrospectively studied by transmission electron mic roscopy nine cases of porphyria cutanea tarda (PCT) that demonstrated caterpillar bodies. We identified three components of the eosinophilic bodies: degenerating keratinocytes, colloid bodies, and basement memb rane bodies. The colloid bodies consisted of whorled masses of filamen ts containing degenerating melanosomes, vacuoles, mitochondria, and de smosomes. Basement membrane bodies were composed of convoluted basemen t membrane material and associated collagen. Both colloid and basement membrane bodies were often associated with degenerating keratinocytes , were located both intra and extracellularly, and were occasionally f used to one another. We believe that caterpillar bodies are a combinat ion of degenerating keratinocytes, colloid bodies, and basement membra ne bodies formed by repeated blistering and reepithelialization with t ransepidermal migration. Furthermore, we believe that caterpillar bodi es are a diagnostic clue for the diagnosis of PCT.