HSP is a multisystem disease with renal, gastrointestinal and
cutaneous manifestations. It usually affects children 5-15 years old with a
slight preponderance of males. Full recovery is common in children. But in
adults, the course could be problematic. Renal involvement is documented
in 10-30% of the cases, but in some series, it reaches up to 90% of the
cases. The primary abnormality is most probably defective handling of
mucosally presented antigen.
Pathology (Fig. 3.9):
There is a great similarity between HSP and IgA nephropathy.
Light microscopy usually shows changes variable from minimal
abnormalities, mesangial proliferation, focal mesangial proliferation with
crescent formation to membranoproliferative glomerulonephritis.
Immunofluorescent microscopy will show predominant IgA deposits
which are mainly mesangial, and this is usually accompanied with C3, IgG
and to a lesser extent IgM.
Clinical features:
1- The disease usually occurs in winter, following upper respiratory
infection or following exposure to allergen.
2- Renal manifestations varies from haematuria (macroscopic or
microscopic), N.S., to RPGN. Severe forms of the disease are more
encountered in adults.
3- Extrarenal manifestations include:
a. Purpuric rash which involves mainly the buttocks and lower
limbs. It does not blanch on pressure and may extend to other
areas.
b. Polyarthralgia or arthritis.
c. Gastrointestinal manifestations including abdominal pain,
bloody diarrhea and or melena.