Differential Diagnosis for Perianal Itching and Dizziness

• Single Most Likely Diagnosis
  • Pruritus ani: This condition is characterized by intense itching around the anus, which can be exacerbated by moisture, friction, and certain foods. The patient's history of perianal itching that worsens with wetness, prolonged wearing of pants, and after using the toilet, along with a previous experience of a similar sensation due to a fungal infection, supports this diagnosis. The absence of a rash and the presence of soft, macerated skin that comes off with scratching also align with pruritus ani.
• Other Likely Diagnoses
  • Haemorrhoidal irritation: Given the patient's history of haemorrhoids, it's possible that the itching is related to irritation from these haemorrhoids, especially if they are thrombosed or prolapsed.
  • Contact dermatitis: This could be due to an allergic reaction or irritation from soaps, wipes, or other products used in the perianal area, which might explain the burning sensation after washing with warm water.
  • Vulvovaginal candidiasis (recurrent): Although the patient denies any current vaginal discharge or burning, her history of recurrent vulvovaginal fungal infections could suggest a possible extension or spread of the infection to the perianal area, causing itching.
• Do Not Miss Diagnoses
  • Anal fissure: While the patient does not report any pain during defecation, which is a common symptom of anal fissures, the possibility of an anal fissure causing itching and discomfort should not be overlooked, especially if there's associated bleeding.
  • Inflammatory bowel disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause perianal itching among other symptoms. Although less likely given the patient's presentation, missing a diagnosis of IBD could have significant implications for the patient's health.
  • Neurological causes of itching: Certain neurological conditions can cause itching without a rash. While the patient's dizziness might seem unrelated, in some cases, neurological issues could explain both symptoms.
• Rare Diagnoses
  • Zinc deficiency: Can cause skin lesions and itching, though this would be less common and typically associated with other systemic symptoms.
  • Diabetes mellitus: Can lead to itching due to dry skin or poor circulation, but would typically be associated with other symptoms such as polyuria, polydipsia, and weight loss.
  • Psychogenic itching: A condition where the itching is of psychological origin, which might be considered if other diagnoses are ruled out and there are suggestive psychological factors.