Thin basement membrane disease is, along with IgA nephropathy, the most common cause of hematuria without other symptoms. The only abnormal finding in this disease is a thinning of the basement membrane of the glomeruli in the kidneys. Its importance lies in the fact that it has a benign prognosis, with patients maintaining a normal kidney function throughout their lives. Signs and symptoms
Most patients with thin basement membrane disease are incidentally discovered to have microscopic hematuria on urinalysis. The blood pressure, kidney function, and the urinary protein excretion are usually normal. Mild proteinuria (less than 1.5 g/day) and hypertension are seen in a small minority of patients. Frank hematuria and loin pain should prompt a search for another cause, such as  kidney stones or loin pain-hematuria syndrome. Also, there are no systemic manifestations, so presence of hearing impairment or visual impairment should prompt a search for hereditary nephritis such as Alport syndrome. Genetics
The molecular basis for thin basement membrane disease has yet to be elucidated fully; however, defects in type IV collagen have been reported in some families.Some individuals with TBMD are thought to be carriers for genes that cause Alport syndrome. Diagnosis
Thin basement membrane disease must be differentiated from the other two common causes of glomerular hematuria, IgA nephropathy and Alport syndrome. The history and presentation are helpful in this regard:
In Alport syndrome, there is often a family history of kidney failure, which may be associated with hearing impairment.
Trichoepithelioma is a neoplasm of the adnexa of the skin. Its appearance is similar to basal cell carcinoma. One form has been mapped to chromosome 9p21. Types
Trichoepitheliomas may be divided into the following types:: 672 
Multiple familial trichoepithelioma
Solitary trichoepithelioma
Desmoplastic trichoepithelioma

Pathology
Trichoepitheliomas consists of nests of basaloid cells, with palisading. They lack the myxoid stroma and artefactual clefting seen in basal cell carcinoma. Mitoses are uncommon when compared to basal cell carcinoma. Diagnosis
Trichoepiteliomas often contain Merkel cells; an immunostain for CK20 can be used to demonstrate this. See also
Trichoblastoma
Pilomatricoma
CYLD cutaneous syndrome
List of cutaneous conditions
List of cutaneous neoplasms associated with systemic syndromes

References


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