Sorted By Test Name - Mayo Medical Laboratories

HMBSK
61217
HCMM
89047
latent periods, and also confirms a biochemical diagnosis during acute episodes. However, a normal result
does not completely exclude a diagnosis of HMBS deficiency/AIP. The preferred diagnostic test is
molecular genetic testing of the HMBS gene.
Useful For: Confirming a diagnosis of hydroxymethylbilane synthase deficiency/acute intermittent
porphyria
Interpretation: An interpretive report will be provided.
Reference Values:
An interpretive report will be provided
Clinical References: 1. Thunell S: Hydroxymethylbilane Synthase Deficiency. In GeneReviews
(Internet). Edited by RA Pagon, TD Bird, CR Dolan, K Stephens. University of Washington, Seattle WA;
1993-2005 Sep27 (updated 2011 Sep 01) 2. Siegesmund M, van Tuyll van Serooskerken AM,
Poblete-Gutierrez P, Frank J: The acute hepatic porphyrias: current status and future challenges. Best
Pract Res Clin Gastroenterol 2010 Oct;24(5):593-605 3. Anderson KE, Bloomer JR, Bonkovsky HL et al:
Recommendations for the diagnosis and treatment of the acute porphyrias. Ann Intern Med 2005 Mar
15;142(6):439-450
HMBS Gene, Known Mutation
Clinical Information: Hydroxymethylbilane synthase (HMBS) deficiency is an autosomal dominant
disorder with incomplete penetrance that can present as acute intermittent porphyria (AIP). The most
common clinical presentation of AIP is abdominal pain. Acute attacks can include vomiting, diarrhea,
constipation, urinary retention, acute episodes of neuropathic symptoms, psychiatric symptoms, seizures,
respiratory paralysis, tachycardia, and hypertension. Respiratory paralysis can progress to coma and
death. HMBS deficiency can also be without clinical or biochemical manifestations. Acute attacks may be
prevented by avoiding both endogenous and exogenous triggers. These triggers include porphyrogenic
drugs, hormonal contraceptives, fasting, alcohol, tobacco, and cannabis. The measurement of
porphobilinogen deaminase (PBG-D) enzyme activity in erythrocytes facilitates detection of AIP during
latent periods, and also confirms a biochemical diagnosis during acute episodes. However, a normal result
does not completely exclude a diagnosis of HMBS deficiency/AIP. The preferred diagnostic test is
molecular genetic testing of the HMBS gene.
Useful For: Diagnostic confirmation of hydroxymethylbilane synthase (HMBS) deficiency when a
familial mutation has been previously identified Carrier screening of at-risk individuals when a mutation
in the HMBS gene has been identified in an affected family member
Interpretation: An interpretive report will be provided.
Reference Values:
An interpretive report will be provided
Clinical References: 1. Thunell S: Hydroxymethylbilane Synthase Deficiency. In GeneReviews
(Internet). Edited by RA Pagon, TD Bird, CR Dolan, K Stephens. University of Washington, Seattle WA;
1993-2005 Sep27 (updated 2011 Sep 01) 2. Siegesmund M, van Tuyll van Serooskerken AM,
Poblete-Gutierrez P, Frank J: The acute hepatic porphyrias: current status and future challenges. Best
Pract Res Clin Gastroenterol 2010 Oct;24(5):593-605 3. Anderson KE, Bloomer JR, Bonkovsky HL, et al:
Recommendations for the diagnosis and treatment of the acute porphyrias. Ann Intern Med 2005 Mar
15;142(6):439-450
Homocysteine (Total), Methylmalonic Acid, and Methylcitric
Acid, Blood Spots
Clinical Information: Homocystinuria is an autosomal recessive disorder caused by a deficiency in
cystathionine beta-synthase. This enzyme is involved in the condensation of homocysteine and serine to
form cystathionine as part of methionine metabolism. The incidence of homocystinuria is approximately 1
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