Pruritis (Diffuse) – 2

Last time we discussed conditions which caused both itching and skin rash.  Today we’ll address pruritis without any visible lesions present, & the patient insists that they never see any.  Once again, our basic differential:

Diffuse Pruritis  —  Differential Diagnosis

Skin Lesions Noted

No Rash or Lesions

  • Allergy without hives
  • Dermatographism
  • Xerosis (Dry Skin)
  • Biliary Tract disorders
  • Hodgkin’s / Hematologic Cancers
  • Blood Dyscrasias
  • Uremia
  • Hyperthyroidism
  • Dermatomyositis
  • Neuro Diseases (rare)
  • Psychogenic

URTICARIA  —  Can’t really say this, without seeing hives, but most acute-onset diffuse itching is IgE-mediated allergy to something.  Go through the same inventory of culprits we mentioned last post.  Give a non-sedating anti-histamine, perhaps also with a sedating one p.r.n. at night.  If itching rapidly ceases, the diagnosis is probably right.

DERMATOGRAPHISM  —  Often occurs along with urticaria, but can be its own independent condition.  Stroke the skin with a tongue depressor, & you generate a beautiful itchy welt.  It often appears within a minute, but may take up to 30.  Treatment is a non-sedating antihistamine.

DRY SKIN (Xerosis)  —  A common cause of mild itchy sensations, especially in low humidity.  More common in the elderly, especially when indoor heaters are in use.  Sometimes the skin looks dry & scaly.  Try an emollient lotion with lanolin.  But if itching is intense, & your treatment fails, strongly doubt the diagnosis.  May order a TSH to R/O Hypothyroidism, but probably have to seek further.

None of Above

The above diagnoses have been entertained, treatment doesn’t help, & significant itching persists.  Unfortunately, some serious diseases might be responsible.  Use your differential to examine for clues, but you’re pretty much stuck doing some sort of work-up.

HODGKIN LYMPHOMA is the most common systemic illness to manifest with isolated pruritis.  Ask about “B-Symptoms”: fevers, night sweats, weight loss.  In terms of “night sweats,” they have to be truly drenching.  I inquire if pajamas or sheets are soaked, then pantomime wringing them out & ask, “Do you see drops of sweat drip?”  Anything less gets charted, “No Night Sweats,” or “minor  night sweats, not drenching.”

Look for splenomegaly, and especially perform a thorough lymph node exam.  What’s the most ominous node in the body?  If you find it, obtain a fine needle aspiration (FNA).  If that’s negative, the node is so suspicious that I’d even arrange an excisional biopsy.

Answer:  the Left SupraclavicularNode!  Long known as the “Sentinel Node” (unrelated to breast cancer or melanoma mapping).  Not the right, which only drains the right thorax.  On the left, the asymmetric Thoracic Duct channels lymph from the entire abdomen & pelvis through it, as well as left chest.  So ovarian and a host of other (metastatic) cancers may first appear as a left supraclavicular lump.

Unfortunately, Hodgkin-associated generalized pruritis can precede other manifestations by up to five years.  I order a CBC, Sed Rate, and even Chest X-ray (for hilar & mediastinal adenopathy) as part of my work-up.  But I wouldn’t obtain an abdominal CT unless the patient had B-Symptoms or other suspicious findings.

Check the weight on every follow-up.  However, as honest as I try to be with patients, I confess that I don’t tell those with generalized pruritis, “it could be lymphoma, but we won’t know for a number of years.”  I do of course reassure them that their exam & labs are normal.

BILIARY TRACT DISEASE  —  Cholestasis commonly causes diffuse pruritis.  If you hear that the itching began in the hands & feet, you can be almost certain.  The two most common disorders responsible are Primary Biliary Cirrhosis (PBC) & Cholestasis of Pregnancy; the latter is an easy diagnosis since it occurs 3rd Trimester.  A host of other hepatobiliary conditions are also possible.

Rule these out by ordering liver function tests (LFTs), especially the Alkaline Phosphatase.  If that’s elevated, obtain an Anti-Mitochondrial Antibody (AMA) for PBC.  But also establish that the high Alk Phos is due to a hepatobiliary condition, and not the bone, intestinal, or placental fraction.  Determine this by drawing either a Gamma-glutamyl transpeptidase (GGT) or a 5-prime nucleotidase (5´ NT).

Order them plus repeat LFTs fasting.  If the Alk Phos normalizes, the prior elevation was due to a post-prandial intestinal fraction.  If the GGT or 5´ NT are high, the Alk Phos is of liver/biliary origin; otherwise, it’s bone (you can always order a urine pregnancy test to be sure it’s not placental).  See the very end of our topic Chronic Hepatitis.

BLOOD DYSCRASIAS  —  These include leukemia, polycythemia vera, multiple myeloma, & mastocytosis, and maybe other lymphomas besides Hodgkin.  All uncommon.  A CBC and Sed Rate will be helpful for rule-outs; if the serum globulin is elevated, order a serum protein electrophoresis (SPEP) for multiple myeloma.  For mastocytosis, inquire about paroxysms of intense itching & flushing (without hives!).

UREMIA  —  Generalized pruritis commonly afflicts Uremic patients, with end-stage renal disease.  Not those with just a slightly elevated creatinine.

HYPERTHYROIDISM  —  An easy diagnosis if you remember to order a TSH.

DERMATOMYOSITIS (DM)  —  Many patients with established DM & Scleroderma complain of pruritis.  It would be reasonable to work these conditions up if a patient complaining of pruritis also describes proximal weakness or unusually rashes (DM), or has evidence of arthralgias, Raynaud’s, skin changes, or other manifestations of Scleroderma.

  • For DM: ↑ ESR, ↑ ANA, ↑ Muscle Enzymes (CK, AST, LDH, Aldolase)
  • For Scleroderma:  ↑ ANA

If labs are suggestive, send to Rheumatology.

PSYCHOGENIC PRURITIS  —  Various entities fall in this category.  Pathologic skin picking may be an obsessive-compulsive manifestation, or be due to the psychotic paranoia of chronic methamphetamine.  Such patients are usually aware of their behavior, and don’t present with pruritis per se, though an examiner may well notice a variety of diffuse scabbed and crusted lesions.

Schizophrenia can manifest with delusions of parasitosis.  Such patients freely acknowledge their insects; the dilemma is more therapeutic than diagnostic.

SUMMARY

A patient presents with diffuse itching, but no rash.

1.  Test for Dermatographism (stroke small area with tongue blade).
  • If a hive, even just itching, develops, treat with an H1 Blocker (loratadine, etc).
2.  Brief H&P seeking:
  • Proximal muscle weakness, violacious rash (face or hands)  ESR, ANA, Muscle Enzymes (CK, AST, LDH, Aldolase) for Dermatomyositis & refer to Rheum
  • Raynaud’s, arthralgias, skin changes of scleroderma  ANA for Scleroderma & refer to Rheum
  • Suspicious nodes  biopsy for Lymphoma
  • Splenomegaly  CBC, Abdominal CT for Lymphoma
  • Dry Skin  TSH; therapeutic trial of emollients
  • Disordered thinking, obsessions  refer to Psych (also r/o meth abuse)
3.  Suspect Allergy (without hives)
  • Empiric H1 Blocker (loratadine, etc).  If no help, try doxepin.
  • Seek possible causes from common allergens (consider avoidance trial)

If pruritis persists…….

4.  Basic Labs: CBC, Comprehensive Metabolic Panel, TSH, ESR.  Chest X-ray.
  • Seek Dx of Uremia, Hematologic Malignancy, Hyperthyroidism
  • If ↑ Alk. Phos.  Antimitochondrial Ab for Primary Biliary Cirrhosis
  • ↑ Globulin  SPEP for Multiple Myeloma
  • ESR very high  consider Multiple Myeloma, Dermatomyositis.  Consider chest & abdominal CTs for Lymphoma
  • Chest X-ray:  seek adenopathy for Lymphoma
5.  Still no clues:  Refer to Derm
  • Continue to follow for B-symptoms or lymphadenopathy (if they occur, repeat labs & get pan-CT)

That’s it for Pruritis; hope we’ve done more than just scratch the surface.

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