Lumpy, Bumpy, Scary Rash: HSP
Suppose your child developed this rash; how long would you wait before seeing the doctor?
We doctors describe this dramatic rash as “palpable purpura.” Palpable means they are raised; we can feel them when we stroke the skin. Purpura refers to blood outside of vessels. If you press down on the lesions, they do not blanch. Smaller, flat lesions without blanching would be called “petechiae” in doctor-speak. Several conditions can cause this sort of rash. The most problematic, meningococcemia, is a bacterial infection that can kill a previously healthy child in a few hours; we now have a vaccine for this condition that I jabbed into my kids as soon as its approval came through. Scary stuff.
The child in the photo has a less threatening illness, Henoch-Schonlein purpura. HSP is a form of vasculitis or inflammation of the blood vessels. The blood vessels become leaky, allowing blood to escape into the surrounding tissues. Essentially, affected children get bruises all over the place! This process can happen in any organ in the body. Some areas are more commonly involved:
- Skin: As blood leaks into the skin it produces a bruise-like rash called petechiae (when pinpoint in size) or purpura (when larger in size). This rash is often lumpy.
- Joints: Vasculitis in the joint can lead to swelling and pain (arthritis) or pain without swelling (arthralgias).
- Gut: Bleeding into the walls of the stomach and intestines can produce nausea, vomiting, abdominal pain, diarrhea, or constipation. Blood in the vomit or stools is not unusual.
- Kidney: Vasculitis in the kidney is given the name glomerulonephritis. Glomeruli are the small tufts of blood vessels that filter our blood to make urine. When inflamed, there may be leaking of blood into the urine (hematuria) and protein into the urine (proteinuria). In severe cases of nephritis, blood pressure may be increased (hypertension), proteinuria may be heavy enough to cause swelling (nephrotic syndrome), or the kidney’s ability to eliminate wastes may be compromised (renal insufficiency or failure).
Other organ systems may be rarely involved. These include the eye, brain, lung, and liver.
The cause of HSP is unknown. Why one person gets it worse than another is also unknown. Seems we don’t know a whole lot of things about HSP!
There is no specific test for HSP. Your doctor makes the diagnosis based on typical findings described above. Often other forms of vasculitis may be ruled out with blood tests or, in extreme cases, a biopsy of the skin. HSP vasculitis looks different from other types under the microscope. Even if there is no evidence of involvement of the kidney, blood and urine tests are usually obtained to look for this complication.
With severe or unusual involvement of any organ system, more tests may be needed. Often a specialist is consulted. For severe renal involvement, a kidney biopsy may be necessary to confirm the diagnosis as HSP and guide further treatment.
Most cases of HSP produce uncomfortable but non-life-threatening problems that come and go for up to 6 months with no specific treatment. Acetaminophen (Tylenol(R)) or other medicines may be used for pain control, but HSP usually goes away on its own.
Long-term problems from HSP are most often caused by bad glomerulonephritis. Treatment for this often includes intravenous and oral steroids (drugs such as prednisone, not the muscle-building steroids) and chemotherapy drugs such as cyclophosphamide. These treatments can stop the inflammation of the blood vessels and prevent permanent kidney failure from developing. Control of high blood pressure is also very important in preventing kidney failure.
The NIH now has a nice page with more information about HSP.