The hematoxylin-eosin–stained punch biopsy specimen revealed mild acanthosis and hyperkeratosis, with a predominance of parakeratosis and mild perivascular infiltration of the upper dermis. Biotinidase activity was reduced to 50% and 26% (reference value, 8.4 nmol/min per milliliter) in the patient’s father and mother, respectively. Carboxylase activity was determined in a sample of the patient’s lymphocytes, revealing a significant reduction of propionyl-CoA [coenzyme A] carboxylase, β-methylcrotonyl-CoA carboxylase, and pyruvate carboxylase to 26%, 36%, and 54%, respectively, of the levels seen in a normal unrelated control sample. Quantitative serum amino acid values were normal, and a urinary organic acid screen revealed mildly elevated concentrations of β-methylcrotonylglycine and methylcitrate. The results of the rest of the laboratory studies, including complete blood cell count, differential cell count, standard chemistry panel, and liver function tests, were normal.
Facial Erythema and Onychoschizia—Diagnosis. Arch Dermatol. 2005;141(11):1457-1462. doi:10.1001/archderm.141.11.1457-e