Alopecia is the absence of the hair from skin areas where it normally is present. There are several types of alopecia, each with their own characteristic appearance and cause(s).
Telogen effluvium can be postpartum or caused by drugs (oral contraceptives, anticoagulants, retinoids, beta blockers, chemotherapeutic agents, interferon), stress (physical or psychological), hormonal (hypo- or hyperthyroidism, hypopituitarism), nutritional (malnutrition, iron deficiency, zinc deficiency), or diffuse alopecia areata.
Anagen effluvium can be caused by Mycosis fungoides, X-ray treatment, drugs (chemotherapeutic agents, allopurinol, levodopa, bromocriptine), or poisoning (bismuth, arsenic, gold, boric acid, thallium).
Cicatricial alopecia can be caused by congenital and developmental defects, infection (leprosy, syphilis, varicella-zoster, cutaneous leishmaniasis), basal cell carcinoma, epidermal nevi, physical agents (acids and alkali, burns, freezing, radiodermatitis), cicatricial pemphigoid, lichen planus, or sarcoidosis.
Androgenic alopecia can be caused by adrenal hyperplasia, polycystic ovaries, ovarian hyperplasia, carcinoid, pituitary hyperplasia, or drugs (testosterone, danazole, ACTH, anabolic steroids, progesterones)
Alopecia areata can be idiopathic (of unknown cause), but may be autoimmune in nature. Traction alopecia can be caused by trichotillomania (direct self-pulling of the hair) or tight rollers or braids.
Tinea capitis can be caused by fungal infection with Microsporum species or Trichophyton species.
Standard labs include thyroid function tests, complete blood count, free testosterone and DHEA-S in women with androgenic alopecia, Serum ferritin, VDRL or RPR for syphilis, and Lymphocyte T and B cell numbers (which are sometimes low in patients with alopecia areata)
A potassium hydroxide (KOH) examination of the scale, if present, will be positive in tinea capitis. A fungal culture of the scale may identify the causitive species.
A scalp biopsy with routine microscopy and direct immunofluorescence will aid in the diagnosis of tinea capitis, diffuse alopecia areata, and the scarring alopecias due to lupus erythematosus, lichen planus, and sarcoidosis. A microscopic examination of the hair shaft may be ordered.
The light hair-pull test will be positive in alopecia areata.
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