Table 3.

Differential diagnosis of classic dengue fever associated morbilliform eruption

Disease	Incubation/presenting symptoms	Morphology	Distribution of rash	Associated findings	Laboratory findings
Measles	8-12 days, rhinitis, cough, fever	Erythematous macules and papules, later becomes confluent	Begins on neck and face, spreads down and become generalized and as it fades it leaves a brownish hue with fine desquamation	Koplik's spots, exudative conjunctivitis, photophobia, pneumonia	Leucopenia, low ESR, IgM positive (measles, immunoglobulin)
German measles (Rubella)	14-23 days, mild URI, fever, eye pain, lymphadenopathy	Pinpoint maculopapular rash	Begins on face and spreads to trunk and extremities	Tender cervical lymphadenopathy, transient polyarthralgia and polyarthritis irritability, febrile seizures	Nasal culture for virus antibody titers
Roseola (Exanthem subitum HHV-6)	5-15 days, high fever for 3-5 days, diarrhea, cough	Pale pink macules and papules	Trunk, neck and proximal extremities		Leucocytosis at the onset and leucopenia later
Infectious mono-nucleosis	Fever, malaise	Polymorphic macularerythema ± petechiae, urticaria, erythema multiforme like lesions	Generalized	Pharyngitis, lymphadenopathy, pinhead petechiae at the junction of soft and hard palate (Forschheimer's spots)	Leukocytosis, atypical lymphocytes LFT (transaminases and bilirubin) may be elevated, serology for heterophilic antibodies positive
Secondary syphilis	Fever, headache, pharyngitis	Polymorphic macules/papules/psoriasiform papules	Generalized	Lymphadenopathy ± condyloma lata ± moth eaten alopecia	VDRL positive
Typhoid fever	Fever, vomiting, diarrhea, headache	2-3 mm pink grouped papules (Rose spots) generalized erythema “erythema typhosum”	Generalized, trunk		Rose spot cultures may be Salmonella typhi positive
Chikungunya fever	3-12 days, fever, arthralgia, myalgia, headache, vomiting	Flushing erythema maculopapular lesions, ± petechiae	Trunk and extremities	Severe joint pains, conjunctival injection	Normal CBC, raised ESR, raised C-reactive protein, Chikungunya IgM positive
Lepto-spirosis	Acute phase: Fever, headache, myalgia, pharyngitis	Morbilliform rash	Generalized	Immune phase: hemorrhage, jaundice, organ failure	Leukocytosis, microscopic agglutination test is positive
Acute retroviral syndrome (HIV)	Fever, fatigue headache	Maculopapular rash	Trunk and upper arms ± palms and soles	Myalgia, lymphadenopathy	HIV RNA, P24 antigen
Rocky mountain spotted fever	3-12 days, fever, malaise, headache	Erythematous macules, evolves to petechiae and purpura	Begins on wrist, ankles; spreads centrally; seen on palms and soles	Hepatosplenomegaly, hyponatremia, myalgias, CNS involve ment	Rickettsial group specific serologic tests positive
Drug exanthem	4-6 days, fever, malaise	Maculopapular or urticarial	Generalized symmetric often spares the face, palms and soles may be involved	Periorbital edema, fever	ESR is low