Clinical use
The test is used to diagnose porphyrias, a group of rare disorders
Background
Porphyrias are a group of rare disorders passed down through families, in which an important part of hemoglobin, heme, is not made properly. Heme is also found in myoglobin, a protein found in certain muscles. Normally, the body makes heme in a multi-step process and porphyrin’s are made during several steps of this process. Patients with porphyria have a deficiency of certain enzymes required for this process. This causes abnormal amounts of porphyrins or related chemicals to build up in the body. There are many different forms of porphyria. The most common type is porphyria cutanea tarda (PCT). Drugs, infection, alcohol, and hormones such as estrogen may trigger attacks of certain types of porphyria.
Porphyrias involve three major symptoms:
- Abdominal pain or cramping (only in some forms of the disease)
- Light sensitivity causing rashes, blistering, and scarring of the skin (Photodermatitis)
- Problems with the nervous system and muscles (seizures, mental disturbances, nerve damage).
Attacks can occur suddenly, usually with severe abdominal pain followed by vomiting and constipation. Being out in the sun can cause pain, sensations of heat, blistering, and skin redness and swelling. Urine may turn red or brown after an attack. Other symptoms may include: muscle pain, muscle weakness or paralysis, numbness or tingling, pain in the arms or legs, pain in the back & personality changes.
Reference ranges
| Faeces | ||
|---|---|---|
| Hepatcarboxylate Porphyrin | FHCP | Normally undetectable |
| Hexacarboxylate Porphyrin | FHXP | Normally undetectable |
| Pentacarboxylate Porphyrin | FPCP | Normally undetectable |
| Isocoporphyrin | ISOC | Normally undetectable |
| Coproporphyrin 1 | FCP1 | nmol/g |
| Coproporphyrin 3 | FCP3 | nmol/g |
| Total coproporphyrin | TCPOR | 0 – 46 nmol/g |
| Dicarboxylate porphyrin | DXP | 0 – 134 nmol/g |
| Faecal total porphyrin | FTPOR | 0 – 50 nmol/g |
| Red Blood Cells | ||
| Erythrocyte Free Protoporphyrin | EFP | 0 – 200 nmol/L cells |
| Erythrocyte Zinc Protoporphyrin | EZP | 0 – 800 nmol/L cells |
| Urine 24 HR | ||
| 5 – Aminolaevulinic Acid (ALA) | ALA24 | 0 – 46 umol/24hr |
| Porphobilinogen (PBG) | PBG24 | 0 – 9 umol/24hr |
| Total Porphyrin | TPOR | 0 – 410 nmol/mmol creat |
| Erythrocyte Hydroxymethyl Bilane Synthase | HMBS | 20 – 42 |
Specimen requirements
Specimen type to be referred depends upon relevant clinical symptoms of the patient. See Table below, if in doubt consult with Clinical Biochemist or Senior BMS.
| Faeces | Small specimen (approx. 10g) |
|---|---|
| Plasma | Lithium Heparin (dark green top) or EDTA (purple top) tube |
| Red Blood Cell | Heparin or EDTA tube |
| Urine | Random collected into a plain universal container OR a 25ml aliquot of a 24hr collection with no preservative |
ALL SPECIMENS SHOULD BE PROTECTED FROM LIGHT DURING COLLECTION, TRANSPORT TO LAB AND SUBSEQUENT STORAGE.
Turnaround time
4 weeks
Additional Information
The following supporting information should be included on request forms.
- Whether patient was symptomatic when the specimens were collected.
- Nature of symptoms i.e. dermatological or neurological.
- If part of family study, the name of the index case.
Referred test
Referred test
Location
King’s College Hospital