A 32-year-old lady comes in with the chief complaint of itching in the groin and in the natal cleft, i.e., between the two buttocks and also some itching in between her finger in the web spaces. She denies any alcoholism. She denies any family history of kidney disease or past medical history of kidney disease. Her lab tests are normal which include CBC, LFT, and renal function. The patient also complains about the itching being worse at night. She denies any problems with her bowel movement. On examination she appears generally well.  She is well built and there are some reddish lesions in between two fingers with some dark spots and a similar pattern in the groin.

Now there are few features in this case, which are important:

1. The itching is worse at night, typically this has been associated with scabies but now we know that almost every itching sensation is worse at night. Only that scabies gets much-much worse at night and almost does not allow the patient to fall asleep. The flexor surfaces are the favorites for Sarcoptes scabiei and thus the lesions can be found in the elbows and between the buttocks, in the groin, in the web spaces, and in the neck. But never are the lesions found about the jawline (except in children). Thus the scalp is spared and the face is spared.

Other itchy lesions to be considered are Pityriasis Rosea, lichen planus, dermatitis herpetiformis, eczema or ectopic dermatitis, and contact dermatitis. The flexor surfaces are typically atopic dermatitis as well as contact dermatitis. The others include dermatitis herpetiformis. This one looks like herpes itself because it has vesicular lesions and, as we know it is associated with the celiac disease or gluten enteropathy.

Lichen planus has flat plaque like lesions as the psoriasis and both of them are slightly scaly. Psoriasis being very scaly and lichen planus having a very light scale as does Pityriasis Rosea having a very light scale. Pityriasis Rosea can sometimes resemble tinea corporis but these lesions are not favorites in the flexor surfaces. Herpes zoster itself does not enter the differential diagnosis as it is usually present in only one area and is unilateral. HIV or other immune deficiency patients may have lesions in multiple zones but that too is unusual.

The patient’s renal function has been mentioned to be normal and that is important because uremia also causes itching or generalized pruritis and as does abnormal liver function but typically associated with severe jaundice and in those cases cholestyramine is of help.

Another cause of itching is neurodermatitis in which the patient has no pathology but feels that he or she has itching and in those cases the patient almost scratches the skin away to form ulcerating lesions. This is not malingering but actually the patient does feel that something is there and continues to go ahead into this. The treatment of this is steroid creams covering the area and also sometimes intralesional injections of steroids.

The treatment of lichen planus is just to watch. Lichen planus also comes with lesions inside the mouth, which are called Wickham’s striae. Lichen planus continues for many years where as Pityriasis Rosea is associated with a Herald patch to begin with which usually is a 2-inch size patch somewhere on the trunk followed by multiple lesions which have Christmas tree appearance. This condition is self-limiting. Steroids may be used to calm down the intensity of the lesion and itching associated with it. One can expect it to last around six months.

Psoriasis as we know is a chronic disorder. One type of psoriasis is important to mention here, i.e., guttate psoriasis because it is frequently shown there are small little lesions which are less than 1 cm in size and are multiple and are distributed all over the body and typically follow an episode of streptococcal infection or a throat infection. This is a self-limiting disease but in 30% of such cases later on in life plaque psoriasis or other form of psoriasis might arise. The treatment of psoriasis will be discussed elsewhere but just a brush on it I think ultraviolet therapy, Psoralens and occasional use of steroid creams is helpful.
Oral steroids can initially curb the lesion but as soon as one decreases the dose of these one can end up with pustular psoriasis where the lesions are full of purulent material. This is why one should avoid the use of oral steroids in psoriasis. A new medication called psoriataine is quite helpful. Methotrexate can improve plaques of psoriasis and also arthropathy related with it. This should pretty much cover most causes of itching in patients.

Anemia and polycythemia, both cause itching as do hypo and hyperthyroidism.

If there is any other cause that you would like to be discussed please write back to me.