History:

 This 65 year old very fat patient came with this nonpruritic hyperpigmented , slightly keratotic plaque on left forearm, extensor aspect since last 1 year. It was completely asymptomatic but patient was anxious about it. It was looking like callosity. I gave him idea that this is a callosity and something is rubbing there. Even after asking many questions I could not come to any conclusion about the cause of the callosity. I told him to be vigilant about any occasion of friction on that area. In his next visit he asked me whether friction of commode edge  while washing anal area after defecation be the cause for callosity. As the patient was very obese he could barely pass his left hand inside commode while sitting on it. That was the cause of the friction.