A 42-year-old male patient presents with odynophagia. He has a background of COPD and HIV (human immunodeficiency virus) and has been non-compliant with anti-retroviral medication for the last 4-5 years. Among other tests he undergoes a barium swallow. The oesophagus is grossly abnormal, the majority of which has a ‘shaggy’ appearance but there are also several more discrete linear plaque-like lesions.

What is the most likely diagnosis?