This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
All the following are primary cutaneous diseases except: 
Select and explain. 
A. Psoriasis, B. Reiter's disease, C. Lichen planus, D. Icthiosis/Bowen's disease
B: Reiter's disease
Answer: B: Reiter's disease 
Explanation: B i.e. Reiter's disease: Reiter's disease or syndrome is primarly a reactive polyahritisQ characterized by presence of non suppurative, painful, asymmetrical oligoahritis with or without urethritis, ureitis, conjunctivitis, oral ulcers and secondary cutaneous involvement in form of rashQ. Psoriasis, Bowen's disease (squamous cell carcinoma in situ), lichen planus and icthyosis are primary cutaneous diseases.