Diagnosis of Atypical HUS Using Genetic Testing

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Figure 1.
Peripheral blood displaying a significantly low platelet count (42,000/uL) and shistocyes. 100X magnification.

Table 1.

Diagnostic timeline

Test	Patient Result						Reference Range
	Day 1	Day 5	Day 10	Day 20	Day 30	Day 50
WBC	20.2	14.5	9.6	6.5	8.6	9.0	4.5–11 X 10³/uL
RBC	2.48^{^*}	2.18	2.44	2.53	2.64	2.86	4.0–5.4 X 10⁶/uL
HGB	7.6^{^*}	6.5	7.5	8.2	8.5	9.2	12.0–16.0 g/dL
HCT	24.0^{^*}	19.6	23.2	26.2	27.9	29.6	36.0%–47.0%
PLT	46^{^*}	52	121	143	156	186	150–450 X 10³/uL
DIFF	↑ PMN^{^*}	↑ PMN	↑ PMN1 meta, 1 myelo
RBC morphology	1+ poly1+ decryoOcc. Shisto^{^*}	2+ aniso1+ polyOcc. Shisto	2+ aniso1+ polyOcc. Shisto	3+ aniso1+ macro1+ stomato1+ decryoOcc. Shisto	3+ aniso1+ macroOcc. Shisto
INR	0.9^{^§}	1.3	1.3				1.0
APTT	23.5^{^§}	33.2	33.2				25.1–36.5 s
FIB	229^{^†}	292	635				200–400 mg/dL
FDP	>5, <20^{^†}						<5 ug/mL
SUN	31^{^*}	69	20	29	9	20	7–18 mg/dL
CR	1.9^{^*}	3.5	2.6	7.2	4.2	6.5	0.6–1.3 mg/dL
ALT	79^{^*}	28	19	13	12		13–56 U/L
AST	257^{^*}	59	28	22	23		15–37 U/L
LDH	746^{^*}		778	439	414		84–246 U/L
CK-MB		Low MI probability		No evidence of acute MI
Troponin I		Low MI probability		Developing or subclinical MI
BNP			991		2744		<125 pg.mL
C3		107.0^{^‖}		84.4			90–180 mg/dL
C4		25.7^{^‖}		11.4			10–40 mg/dL
Haptoglobin			8				40–240 mg/dL
Shiga Toxin I		Neg^{^‡}					Negative
Shiga Toxin 2		Neg^{^‡}					Negative
Cl. Diff.		Neg					Negative
ADAMTS13		20^{^#}					>60%
Renal biopsy			Changes consistent with toxemia of pregnancy with progression to frank TMA. Given history of recent pregnancy, this most likely represents HELLP syndrome. However, HUS, aHUS, and TTP cannot be excluded.

Table 2.

aHUS susceptibility panel

Test	Patient Result, Day 10	Reference Range
aHUS susceptibility panelC3, CFB, CFH, CFHR1, CFHR3, CFHR5, CFI, MCP, THBD deletion analysis	Allele 1: Deletion of CFHR3-CFHR1Allele 2: No deletion detected	No deletions detected